What is the probability that the student attends at least one class on Monday?

Question

involving a student's attendance at math and accounting classes on Mondays. Assume that the student attends math class with probability 0.65, skips accounting class with probability 0.25, and attends both with probability 0.45.

What is the probability that the student attends at least one class on Monday?

Answer 1

P[math] = 0.65
P[accounting] = 1 - 0.25 = 0.75
P[math AND accounting] = 0.45

so P[math OR accounting]
= P[math] + P[accounting] - P[math AND accounting]
= 0.65 + 0.75 - 0.45 = 0.85

ans: 0.95 or 95 %