$A$ and $B$ are mutually exclusive, $P(A) = 0.35$ and $P(A \cup B) = 0.8$. What is $P(B)$?

Explanation

1. 01

   For mutually exclusive events, $P(A \cup B) = P(A) + P(B)$.

2. 02

   $0.8 = 0.35 + P(B)$, so $P(B) = 0.45$.