Given that is a sample space of a random experiment, where , , and , determine .
First, solve or in terms of as follows:
The events and are complementary, so the sum of their
probabilities is equal to 1. Now use this fact to find probability
Next, solve for in terms of .
Since events , , and are mutually exclusive, and they make up
the sample space, the sum of their probabilities must equal 1.
Next, use this fact to find the probability of .
Thus, the probability of is equal to .