Is the Algebraic Manipulation of Set Theory Expressions Accurate?

[Natasha1]

Can anyone just check if I got it right please?
And if so could you just explain the theorems that come with each line? Many many thanks in advance

(A-B) n (B-A) = (AuB’) n (BuA’)
= (Au(BuA’)) u(B’n (BuA’))
= ((AnB) u (AnA’)) u ((B’nB) u (B’nA’))
= (AnB) u Ø u Ø u (B’nA’)
= (AnB) u (B’nA’)
= (AnB) u (BuA)’
= (AnB) - (BuA)
= (AnB) - (AuB)

 

[EnumaElish]

If A = {1,2,3,4} and B = {3,4,5,6}, what is A-B? What is B-A? What is their intersection?