Jane has two tennis serves, a hard serve and a soft serve.
Her hard serve is in (a good serve) 50% of the time, and
Her soft serve is in (good) 75% of the time. If her hard
Serve is in, she wins 75% of her points. If her soft serve is
In, she wins 50% of her points. Since she is allowed to reserve
One time if her first serve is out, what should her
Serving strategy be? That is, should she serve hard followed
By soft; both hard; soft followed by hard; or both

Here, you can draw a probability tree and find the probability in each case. This will show you where does she get the most probability to have high points.