Your tattoo is likely not a proof, but just a formula. And if I am not mistaken: the assumption that the formula is true, got disproven a few years ago.

Dogs are the same. They think they are humans. The first tribe members that clearly know that they are not humans are apes and some monkeys.

No. The teacher did not have it wrong. Does not mean the student is right … Marty and Luis both had their own pizza. Marty had a big pizza and “only” managed to eat 4/6th of it. Luis had a small pizza, and “only” managed to eat 5/6th of his. If you want to give a nitpicking correct answer: a single pizza does not have (4 + 5)/6th pieces. x/6th implies the pizza(s) were divided into 6 parts … so: it can only be 2 pizzas.