1. The problem statement, all variables and given/known data I am trying to prove the absorption law A U (A ∩ B) = A I know that a way to prove this is to show that each is a subset of the other but I'm a little confused about one part in the process (below) 2. Relevant equations 3. The attempt at a solution Let x∈A U (A ∩ B) then x∈A or x∈(A ∩ B) so because x∈A then we know that A U (A ∩ B) ⊆ A (I don't understand why this line is true.) Why just because x∈A does it mean that A U (A ∩ B) ⊆ A is true? Any help is greatly appreciated.