let A and B be subsets of the universal set, prove that: A = AUB IIF B is a subset of A.

Suppose x is in A then x is in (AUB). which implies that B is a subset of A.

conversely Suppose that B is a subset of A, then if x is in B then x is in A. Which implies that x is in AUB = A.

is this proof correct, should i have taken another route, maby proof by contradiction?

it dosent feel like i have proven anything, just restated the problem.

how would you have solved it?

thanks for all help