Question

Artaud noticed that if he took the opposite of his age and adds 40 he gets the number 28 how old is Artaud

Answer 1

Artaud is 12 years old, because

28 = 40 + (-1)(x), x = Artaud's age
-1x +40 = 28
-x = -12
x = 12

You multiply x and -1, because that is how you get the opposite.