Hi I am really stuck with this question... any hints most appreciated

The symmetric difference between two sets is defined as

A (triangle) B = (A-B) U (B-A)

(b) Prove (algebraically) that (A-B) U (B-A) = (AUB) -(AnB)

(c)If A is the set of even integers and B the set of integers which are multiples of 3, describe the set (AUB) - (AnB)