Math Is Fun Forum

Hello everybody

I'm trying really hard to understand these proof methods, but still haven't clear it at all. So could someone explain me the following:

A is a subset of B if and only if A intersection B complement is empty set?

I think that it's not true because of the A intersection B complement ->x is in A, but not in B, so that's empty set. And we have the statement A is subset of B, so x is A and in B.

Thanks