Prove identities involving complementation of sets?

Question

More importantly, 3 and 4.

1. (A ∪ B)^c = A^c ∩ B^c
2. A ∩ [(A ∩ B)^c] = A – B
3. A ∩ [(A ∩ B^c)^c] = A ∩ B
4. (A ∪ B) ∩ (A^c) = B-A

Other stuff:
A ∪ B = A or B
A ∩ B = A and B
A^c = x is not in A

Answer 1

3. A ∩ [(A ∩ B^c)^c]
= A ∩ (A^c U B)
= (A ∩ A^c) U (A ∩ B)
= { } U (A ∩ B)
= (A ∩ B)

4. (A U B) ∩ (A^c)
= (A ∩ A^c) U (B ∩ A^c)
= { } U (B ∩ A^c)
= B - A.