Emily surmises that the probability that she will pass math

Emily surmises that the probability that she will pass math or chemistry is 0.80, the probability of her passing math is 0.57 and the probability of passing both is 045. Find her estimate of the probability of passing chemistry.

Solution

Let A be passing of the subject math and let B be passing of chemistry.

Given :

P(AUB) = 0.80

P(A) = 0.57

P(A int B) = 0.45

Formula : P(B) = P(AUB) - P(A) + P(A int B)

P(B) = 0.80 - 0.57 + 0.45 = 0.68 is the required answer.