Answer:
10% of students buy neither the textbook nor the supplement from the bookstore
Explanation:
We have that:
15% buy only the textbook.
75% buy both the textbook and the supplement.
None buy only the supplement.
a) What percent of students buy neither the textbook nor the supplement from the bookstore
15% + 75% = 90% buy at least one of them. So
100% - 90% = 10% buy neither.