The Son of a Bitch

Akpos was doing his maths homework & 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 ?
Akpors : I'm doing maths homework
Mom : this is how your teacher taught you?
Akpors : 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 teaching them to say 2+2, the Son of a bitch is 4 ?
Teacher after laughing : What I taught them was, 2+2, The Sum of Which is 4