We can use Bayes' theorem and the definition of conditional probability to solve for P[B].

First, find the joint probability P[A ∩ B] using P[B|A]: P[B|A] = P[A ∩ B] / P[A] 0.50 = P[A ∩ B] / 0.30 P[A ∩ B] = 0.50 × 0.30 = 0.15

Next, use the joint probability and P[A|B] to find P[B]: P[A|B] = P[A ∩ B] / P[B] 0.25 = 0.15 / P[B] P[B] = 0.15 / 0.25 = 0.60 or 60%