the son of a bitch

Timi was doing his maths homework was saying:2+5, the son of a bitch is 7. 3+6, the son of a bitch is 9...
His Mom : What are you doing?
Timi : I'm doing maths homework.
Mom : This is how your teacher taught you?
Timi : Yes.
Infuriated, Mom asked the teacher the next day -

'What are you teaching my son in maths?'
Teacher : Right now, we are learning addition.
Mom : You are teaching them to say 2+2, the Son of a bitch is 4?
Teacher : what? I did no such thing....

he called Timi over and asked him what was it he told his mom...
Timi repeats..... 2+5, the son of a bitch is 7. 3+6, the son of a bitch is 9...

Teacher after laughing : What I taught them was, 2+2, The Sum of Which is 4.