These are pretty straight forward using a little common sense and the "fundamental rule of counting": If one thing can happen in n ways and another can happen in m ways they can happen together in nm ways.
If we were to choose the two males first, there would be 10 choices for the first male and 9 choices for the second, then 7 choices for the female so 10(9)(7). However, we do not have to choose in that order. There are 3(2)(1)= 6 orders in which to choose the two males and one female (writing M1 for the one of the males, M2 for the other, and F for the female those 6 orders would be M1M2F, M1FM2, M2M1F, M2FM1, FM1M2, FM2M1) so there are 10(9)(7)(6) ways to do this.(b) 2 males and 1 female from the class
??? How large is the committee? If you mean "form a committee consisting of all the seven females in the class, there would, of course, be one such committee. But I suspect you mean "How many ways to form a committee of "n" people, chosen from the 7 females". To answer that we need to know what "n" is.(c) All females from the class
This is the same as (c) but with males replacing females. How large is the committee to be?(d) No Females