Let $0 < P(A) <1$$,0< P(B) <1$ and $P(A \cup B) =P(A) +P(B) - P(A).P(B)$ Then

Question

$\begin{array}{1 1} P(B/A)=P(B)-P(A) \\ P(A ' \cup B'=:P(A')+P(B') \\ P((A \cup B)'=P(A) \\ P(A/B )=P(A) \end{array}$