Example 2. Toss a coin three times, what is the probability of getting "2 heads and 1 tail"? (Exercise 6, Question 5)
Make a tree diagram:
First time Second time Third time

There are 8 equally likely basic events, and the event $\{2$ heads, 1 tail $\}$ includes 3 basic events, so the required probability is $\frac{3}{8}$.