$P(A) = 0.5$, $P(B) = 0.3$ and $P(A \cap B) = 0.2$. What is $P(A' \mid B')$?

Explanation

1. 01

   $P(A \cup B) = 0.5 + 0.3 - 0.2 = 0.6$, so $P(A' \cap B') = 1 - 0.6 = 0.4$.

2. 02

   $P(B') = 1 - 0.3 = 0.7$, and $P(A' \mid B') = \frac{0.4}{0.7} = \frac{4}{7}$.