P(A∩B)=3/100 = 0.03 = P(B∩A), P(B|A)=3/20 = 0.15 = P(B∩A)/P(A) = 0.03/P(A) 0.15 = 0.03/P(A) 0.15P(A) = 0.03 P(A) =0.03/0.15 = 0.2 = 2/10 = 1/5 Edwin