Answer
$0.5$.
Work Step by Step
The Addition Rule of Probabilities says that: $P(A\cup B)=P(A)+P(B)-P(A\cap B)$. If A and B are mutually exclusive, then $P(A\cap B)=0$.
SOlve for $P(A)$ in the formula above to obtain:
$P(A\cup B)=P(A)+P(B)-P(A\cap B)\\
P(A\cup B)-P(B)+P(A\cap B)=P(A)\\
P(A)=P(A\cup B)-P(B)+P(A\cap B)$
Substitute the given values to obtain:
$P(A)=0.65-0.3+0.15=0.5$.
