A is a set with 6 elements. How many subsets of exactly size 2 does A have? How many subsets of at least size 2 does A have? How many subsets of at most size 2 does A have?

Answer 1

Exactly 2 --> (6 choose 2)

At most 2--> (6 choose 0)+(6 choose 1)+(6 choose 2)

At least 2:

Sum (6 choose n) where n=2,3,4,5,6