Question

Sorry posted the wrong question earlier.

Let A and B be sets. Show that A \ (A \ B) ⊆ B.

Answer 1

A\B is all x in A but not in B

x not in A\B is all x in A&B or in B.

So, A\(A\B) is all x in A and in (A&B or B) so, it is all x in A&B ⊆ B