If , ,
and , determine .
The notation refers to the probability of either event or event occurring, or both. If and are two non-mutually exclusive events,
then , where the notation refers to the probability of events and occurring together.
First, use this fact to determine as follows:
Since and are complementary, the sum of their probabilities is equal to 1. Now use this fact to find the probability of
Thus, is equal to 0.91.