Topic of these question: permutations and combinations : What they give us: A class of students consists of 8 boys and 12 girls.

Three questions we have to answer:

1. Suppose two of the students do not get along. How many ways can a committee of 6 be selected so that the two of them aren't both selected?

2. Suppose two of the students are glued together and cannot be separated. How many ways can a committee of 6 be selected?

3. Suppose the class wants to elect a president, vice president, secretary and treasurer. How many ways can the 4 officers be selected?