PnF 7 times 13 equals 28

One day in Phineas and Ferbs backyard. Buford and Baljeet pay a visit.
Baljeet: Hello friends. What is up?
Phineas: Not much. Just trying to figure out something to do today.
Buford: Oh man. I walked over here it see what you guys were doing for nothing.
Phineas: Don't worry Buford. We'll think of something.
Buford: You better.
Just then, Isabella(in her fireside girls uniform) walks through the gate.
Isabella: Hi Phineas. Whatcha doin?
Phineas: Nothing. What are you doing?
Isabella: The fireside girls and I are trying to sell 28 boxes of our muffins. It shouldn't be to hard cause there is 7 of us.
Buford: There is 7 of you and your trying to sell 28 boxes of muffins?
Isabella: Yep.
Buford: You know each one of you would have to sell like 13 boxes each right?
Isabella, Phineas and Baljeet: What?
Ferb scratches his head.
Buford: Ya, 7 times 13 equals 28.
Baljeet: No Buford, 7 times 4 equals 28.
Buford: No, it's 7 and 13.
Baljeet walks over to Phineas and Ferbs blackboard.
Baljeet: Can I barrow this?
Ferb nods his head and Baljeet wheels it over to the others.
Baljeet: Okay Buford, show us how 7 and 13 equal 28.
Buford: Alright then. I'll divide it.
Baljeet: Okay.
Buford: There's a 7 and here's 28. Now, 7 can't go into 2 so the 2 goes down here for now. Now 7 into 8, once so 8-7=1. We put the 1 over here. Now as for the 2 I didn't use before. It goes her in front of the 1 and we got 21. And 21 divided 7 is 3. Put the 3 behind the 1 and we get 13.
Baljeet(erasing the board): Oh wait that doesn't make sense. What kind of math are you using?
After erasing.
Baljeet: Try multiplying.
Buford: Okay. Here's 7 and 13. Now 7 times 1...
Baljeet: 7
Buford: Right and 7 times 3 is 21. 21 plus 7 is 28.
Baljeet(erasing the board again): Wait a minute, what are you trying to pull?
After erasing the board again.
Baljeet: We'll add this time.
Buford: Fine.
Baljeet: Um…put seven 13s on the board.
Buford(as he is putting up the 13s): 1,2,3,4,5,6,7,8,9,10,11,12,13.
Baljeet: Now wait. Your tell us that all of that adds up to 28?
Buford: Yep.
Phineas: If you can pull that off, I'll….
Buford: Kiss Isabella on the lips.
Phineas stands there thinking.
Phineas: Okay, why not. You don't mind do you Isabella?
Isabella: NO!!! I'm mean sure, okay, no pro here.
Buford: Alright then…
Before Buford could start counting. Baljeet pushes him aside and starts counting himself.
Baljeet: 3,6,9,12,15,18,21.…
Then Buford picks up Baljeet by his underwear and puts him aside and finishes the counting.
Buford: 22,23,24,25,26,27,28. Okay. It's 28, now kiss her.
Phineas: You know your math is still wrong.
Isabella(excited): Oh well Phineas, a deals a deal.
Phineas: Okay.
Phineas stars to move in to kiss Isabella. He closes his eyes as he gets closer and closer. Isabella starts to sweat and get nerves. When Phineas lips were just centimeters from Isabells, Isabella turns all red and faints. Buford laughs like crazy. Baljeet was staring at the blackboard confused and rubs his butt cause of the wedgie Buford give him. Ferb just stands there.
Phineas: Isabella, are you okay?
Isabella just nods.
Phineas: What happened?
Ferb: Well, she either couldn't stand you kissing her on the lips….or she fainted cause of the number of boxes they have to sell.
Phineas: Well, I'm not that bad am I? It's probably the number of boxes to sell.
Buford, Baljeet and Ferb: Sure it is.
And all three roll their eyes.
Phineas: If it will help Isabella. I'll buy a box.
Isabella(with a huge smile on her, still, red face): Thanks Phineas.