This story takes place in an alternate world where Pinkie and Twilight have opposite brains. In this alternate dimension, this takes place before Twilight as we know her became a princess. I hope you enjoy!
The pink pony walked in small circles around the laboratory in her basement. This just doesn't make any sense. If one team of pony workers can complete a job in a total of 9 days, and the second team can complete the same job in 7 days, and if the first team worked for three days, and then the second team joined in... how many days was the job completed? Pinkie Pi thought to herself.
Her unicorn friend Twilight Sparkler became really confused, and was having some trouble with her math. She knew that her magical friend Pinkie would help her.
"Did you find it yet? Do you know what the answer is?" The purple unicorn asked, rocking side to side in a wooden stool.
Instead of answering, Pinkie put on her thick, light blue glasses. Trotting over to her long chalkboard, she immediately began drawing out pictures.
"What's that?" The unicorn asked, jumping off the stool. Now bouncing up and down, she leaped over beside Pinkie. Her big, purple eyes was focused on the drawing of circles and lines on the board, along with a few scribble-looking things.
"What's that thing?" Twilight asked, pointing to an equal sign with a slash through it.
"It's an nonequivalent sign. Did you know that there are about 12 nonequivalent hydrogens in lauric acid?" Pinkie Pi replied, keeping her expression serious as she wrote.
"Oh. What does that mean?" Twilight Sparkler asked, now even more confused than earlier.
"Lauric acid, or also known as systematically dodecanoic acid, is the saturated fat acid with a 12-carbon atom chain, thus falling into the medium chain of fat acids, creating a white, powdery solid with a faint odor of bay oil or soap." Pinkie Pi answered, continuing to draw out the math problem.
"Oooh! And what does that mean?" Twilight asked, a smile still glued to her face.
Pinkie sighed. "You'll learn someday. For now, let's just answer your math problem."
"Alrightie!" Twilight bounced up and down, but unlike when most ponies make a 'thud' noise every time they hit the ground, she barely made a sound. Her eyes stayed on her pink earth pony friend as she began to work out the problem.
"Okay, Twilight. If the first team completed 1/3 of the job working alone for 3 days. That leaves 2/3 of the job remaining, correct?" Pinkie Pi asked rhetorically, her eyes still on the math problem in front of her.
"Uhh... whatever you say!" Twilight continued bouncing.
"So, if I take the 2/3 and rewrite that as a fraction with 9 and 7 days to represent the number of days they supposedly worked..." Pinkie trailed off in into genius talk. Her friend Twilight Sparkler bounced around. The purple unicorn was very interested in the earth pony's lab, even though she came down into this weird room a lot. All around her weird machines beeped and buzzed. Lights flashed on and off. Chalk scratched on the chalkboard. Graphs hung like posters on the wall, and many instruments as big as telescopes down to the smallest microscopes could be found wherever you looked.
Pinkie Pi wrote an new equation on the board. "So, if (1/9) x + (1/7)x = 2/3, then 7x + 9x = (2/3), and then if I have (63)..." Pinkie began mumbling as she wrote.
"Hey! I just had an idea!" Twilight shouted.
"Twilight Sparkler! Hush! I'm trying to work!" Pi said.
"Sorry... hey, can I ask you about it later?" Sparkler asked.
"Yeah, sure. But now, I am doing a math problem. Your math problem." Pinkie Pi continued to draw.
Twilight Sparkler sat down. Her hoof tapped the cold, hard, wooden floor quickly as she waited for her friend to be done.
"Ah-ha! 16x = 42, so if x = 2.625 days, then that means... the total amount of days is 5.625! Ah ha!" Pinkie Pi exclaimed, circling the answer on the now messy looking chalkboard.
"What?" Twilight asked.
"Your answer is 6, Twilight. 6." Pinkie said.
"Oh! Okay. Thanks, Pinkie!" The purple unicorn said. She began walking onto the staircase leading out of the basement.
Twilight Sparkler was about to exit when she remembered she wanted to ask her friend something. "Uh... Pinkie? Can I ask you now?" the unicorn asked.
"Sure. What?" Pinkie replied, cleaning off the chalkboard.
"What if in an alternate dimension somewhere, oh, I don't know... you and I had somehow swapped personalities, and I was smart and you were whatever I am, and if I also at the same time was a princess with wings?"
"I doubt that's possible." Pinkie rolled her eyes.
"Are you sure? I mean, you did this math and all... I don't know. To me, traveling intergalactic dimensions to an opposite world seems easier to me than algebra." The purple pony left the room.
Pinkie sighed. If I was ever as hyped as that pony...
Author's Note
I do NOT own this math problem. I found it here. Also, I have no idea if I did the math right. I am like Twilight Sparkler when it comes to any kind of algebra.
BTW- I highly recommend reading the alternate ending. It will help clear up some of the questions I thought my readers would have, and it also helps the story to overall have a funnier ending.
Twilight Sparkler was about to exit when she remembered she wanted to ask her friend something. "Uh... Pinkie? Can I ask you now?" the unicorn asked.
"Sure. What?" Pinkie replied, cleaning off the chalkboard.
"What if in an alternate dimension somewhere, oh, I don't know... you and I had somehow swapped personalities, and I was smart and you were whatever I am, and if I also at the same time was a princess with wings?"
"I doubt that's possible." Pinkie rolled her eyes.
"Are you sure? I mean, you did this math and all... I don't know. To me, traveling intergalactic dimensions to an opposite world seems easier to me than algebra." The purple pony left the room.
Pinkie sighed. If I was ever as hyped as that pony...
Suddenly, a purple and green little dragon popped his head in."Pinkie? Hey, can I ask you something?"
"I'm at work, Spike. Call me by my work name." The pink pony said, returning to her job at the seismograph machine.
"Sorry." Spike cleared his throat, "Professor Pi, what does it mean if you somehow find a huge black hole in your bedroom wall and all you see through it is rainbow sparkles?"
"Nice comedy, Spike. Now please let me get back to work... this machine detected an earthquake all the way from Unicorn Range. Now, Ponyville could be in trouble, so if you would ple-"
"I'm serious!" Spike said. He was using his serious tone of voice, and his face matched up his emotional complexion.
"Alright, alright, fine. But if this is a joke..." Pinkie followed her assistant up the stairs.
Pinkie gasped as she walked into her bedroom. Sure enough, like Spike had said, there was a huge hole in the wall leading into what looked like outer space.
Pinkie Pi walked towards it, and then stuck her hoof in.
"Pin- I mean Professor! What are you doing?" Spike shouted with worry as the hole sucked in the pink pony.
Pinkie Pi landed in... her house? But, this house was more colorful and bright, unlike her stable, clean, natural-feeling home. Suddenly, she looked up to see her purple unicorn friend Twilight Sparkler, and - herself?
"Do you think she's alright?" The other Pinkie asked.
"Let's do a test. Hello! I'm Twilight Sparkle, and this is my friend Pinkie Pie. Who are you?" The purple pony asked.
"I'm Pinkie Pi. And you're Twilight Sparkler, and you are some sort of impostor!" Pinkie Pi said, facing the other Pinkie Pie.
"Is she from the pool? I thought we got rid of them all..." Pinkie Pie said.
"Excuse me, but I don't think you exactly know what's going on." Twilight changed the subject, hopefully intending for it to be positive.
"I don't I went through a hole in my wall, and now here I am!"
"I think you are from an alternate dimension somewhere, oh, I don't know... you and I had somehow swapped personalities, and I was smart and you were whatever I am, and if Twilight Sparkle here was also at the same time was a princess with wings!" Pinkie Pie said, bouncing up and down.
"How- how did you-" Pinkie Pi stuttered.
"You had better go home before anything damaging happens." Twilight said.
"Before I go back, would you mind turning?" Pi asked.
"Turning?" Twilight was confused.
"Are you a princess?"
"Well, uh, yes." Twilight showed Pinkie Pi her wings.
Pinkie Pi gasped. After facehoofing herself, she went back through the portal.
"Pinkie! What happened?" Spike was anxious.
"Let's just say traveling intergalactic dimensions to an opposite world seems easier to me than algebra at the moment." The earth pony said.
Spike had no idea what just happened to his friend, but somehow with her acting like Twilight Sparkler, she seemed more... natural.
Author's Note
My whole story has been unedited, so if you see any mistakes please let me know nicely in the comments! Thanks! 
