Here's the question you clicked on:
MommyToBe81913
What property of equality allows 7(x - 1) to equal 7x - 7?
I think you looking for the "Distributive Property" http://math.about.com/od/algebra/a/distributive.htm
Well, sorry for posting that. i thought @ritez was still typing but I guess they weren't. I beg your pardon :)