Given: The Probability of at least one of the events A and B occurs = P(A ∪ B) = 0.6 The probability that A and B occur simultaneously = P(A ∩ B) = 0.2 P(A ∪ B) = P(A) + P(B) - P(A ∩ B) 0.6 = P(A) + P(B) - 0.2 P(A) + P(B) = 0.8 P(A)’ = 1 - P(A) ----(1) P(B)’ = 1 - P(B) ----(2) Adding (1) & (2) P(A)’ + P(B’) = 2 - [P(A) + P(B)] = 2 - [0.8] = 2 - 0.8 = 1.2