How do you solve-
this year, 75% of the graduating class of harriet tubman high school had taken at
least 8 math courses. of the remaining class members, 60% had taken 6 or 7 math
courses. what percent of the graduating class had taken fewer than 6 math courses?

If 75% of the students had taken 8 courses, 25% had not. Of these remaining 25%, 60% of them (or 60% of 25% = 15%) had taken 6 or 7 courses. Thus 90% (75% + 15%) of the students had taken 6, 7 or 8 courses.

Thus only 10% had taken less than 6 courses. I hope this helps.