son of a bitch

A little boy was doing his math’s homework. He said to himself, 2+5the son of a bitch is7.. 3+6the son of a bitch is9.
His mother heared this &gasped “wht r u doing?” the little boy answered,”I’m doing my math’s homework,Mom.” “And this is how ur teacher taught u to do it?”
“Yes”he answered.
Infuriated,the mother asked the teacher nxt day, “wt r u teaching my son in math’s?”
The teacher replied,”right nw we r learning addition”
The mother asked,”And r u teaching them to say 2+2,the son of a bitch is 4?”
After the teacher stopped laughing, she answered “wht I taught them was,2+2 THE SUM OF WHICH IS4”:)