8 cups of punch with 15% of sorbet in each cup.
First we have to find out how much 15% makes up in one cup, which is .15
(by moving the decimal two places to the left).
Then we have to multiply .15 by 8 (amount of cups).
.15 * 8 = 1.2
1.2 cups of sorbet were used.
Hope I was able to help :)