Of the fifth-grade students, 20/25 went to the book fair. Of the students that went to the book fair, 8/10 bought at least one book. What fraction of students bought at least one book?

8/10 = 16/20

16/20 out of 20/25 bought at least 1 book.

Put this into words:

16 out of 20 people out of 25 fifth-grade students went out and bought a book.

Makes perfect sense, doesn't it?

16/25 people bought at least 1 book.