1. The problem statement, all variables and given/known data We have three events A, B and C. Find an expression for the probability that exactly one event occur. Note the answer must be written in terms of probabilities of the individual events, probabilities of simultaneous occurrence of pairs of events and the probability of the simultaneous occurrences of all three events. 2. Relevant equations 3. The attempt at a solution So I be honest, I'm actually very confused about this question. I don't understand how to approach it. I think I need to solve for the probability of event A occurring while not B or C. And same thing for B and C. But I'm not sure how to express this. And expressing the probabilities of simultaneous occurrence of pairs of events and the probability of the simultaneous occurrences of three events don't make much sense to me. Any assistance would be greatly appreciated.