What percent of the graduating class had taken fewer than 6 math courses?

Question

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?

Answer 1

75 % took at least 8 math courses

of the remaining class members( 25 % remain ), 60 % took 6 or 7 math courses, thus 60 % of 25 % is

0.6x25 %=15 % took 6 or 7 math courses

so 75 % took 8 or more math courses, 15 % took 6 or 7 math courses, therefore that leaves 10 % taking fewer than 6 math courses ( 75 %+15 %=90 %, 100 %-90 %=10 %)