Hey guys. IF i have Ace,10 the other guy has 7 10.

The flop is 6,7,8,9 and Q.
Who is winning.We almost had a fight over this last nite because the guy said he had a straight plus the pair 7 and he has winning hand.So can you please clear this up for me.And also can you refer me to an official rule to explain this.This is my cuzin and he is still upset so i just want to convince him that he was wrong.
thank you guys.