a young boy is doing his maths homework, his mother listens to him counting and doing his sums, the boy counts,
two plus two this son of a bitch is four
three plus three this son of a bitch is six
his mother angered walks in and asks him where he learnt that sort of language from
the boy replies his maths teacher, the next day the upset mother phones the maths teacher and demands an answer as to what he had been teaching her boy and tells him what the boy had said,
when the teacher finally manages to stop laughing he says
two plus two the sum of which is four.

sometimes what we hear isnt what is said.