The question that I am working on follows:

A class has 10 male students and 7 female students. How many ways can we choose a committee consisting of

(a) 2 students from the class

(b) 2 males and 1 female from the class

(c) All females from the class

(d) No Females

I found this solution that is kind of similar, but I am having trouble understanding it. How do I answer these questions?

Thank you!