The following is the question, working and answer, but could you tell me the reason of the lines with *??

((BA)’ A)
=(B’A’) A
*=(AB’)(AA’)
*=(AB’)U
*=AB’

2. =(B’∩A’) ∪A
Distributive property, similar to 4 * (6 + 3) = 4*6 + 4*3
*=(A∪B’)∩(A∪A’)

(A∪A’) is the universal set: U

*=(A∪B’)∩U

C∩U = C is true for any set C.

*=A∪B’

-O