Well I really can't explain but the answer is 0.32 square millimeters...so sorry if this didn't help.
namely what's 240⅛ - 215⅝.
firstly, let's convert the mixed fractions to improper, and then divide.

This question is a bit confusing, but i would say that the correct answer is f. The sum of the digits would be 3, which isn't divisible by 9.