They work it out with a pencil.
Nevermind, it's pointless.
Because when they are kids their mothers always tell them: "If you grow up you have to work" *Translated from italian hope it makes as much sense as there
Katie Keurig. (I know the setup might need some work but I just like the punchline I made up.)
They're always plotting against it.
Because he's a cross product.
He works it out with a pencil
How does a mathematician cure her constipation She works it out with a pencil.
He who smelt it, dealt it.
He worked it out with a pencil