Proof through inclusion (A∆B) ∪ A = A ∪ B

Hey guys,
Maybe someone of you can help. I need to prove the following through inclusion:
(A?B) ? A = A ? B

Any suggestion on how to solve this?

Answer

Answers can be viewed only if
  1. The questioner was satisfied and accepted the answer, or
  2. The answer was disputed, but the judge evaluated it as 100% correct.
View the answer
The answer is accepted.