Events A and B are such that P(A)=0.7, P(B)=0.2, and P(A∩B)=0.2. Find P(A|B').
I found out that P(A u B) = 0.7, but I'm not sure how to work out the conditional probability – I've tried using the formula and I got P(A|B') = (0.7*0.8)/0.8, but that seems wrong.
Best Answer
$$P(A\mid B')=\frac{P(A\cap B')}{P(B')}=\frac{P(A)-P(A\cap B)}{1-P(B)}$$