Question

Q and R are independent events. P(Q) = 0.4; P(Q AND R) = 0.08. Find P(R).

Answer 1

Because Q and R are independent, you have

$\mathbb P(Q\cap R)=\mathbb P(Q)\times\mathbb P(R)$
$0.08=0.4\times\mathbb P(R)$
$\implies \mathbb P(R)=0.2$