Hello

The remaining class members, who took less than 8 math courses, is 25%.

60% of that 25% had taken 6 or 7 math courses.

Find 60% of 25%:

0.6 x 0.25 = 0.15

So 15% had taken 6 or 7 math courses, that leaves 10% that had taken fewer than 6.

Hope this helps.