A quality control inspector samples 2 computer chips from a box containing 13 computer chips. If the box contains 3 defective chips, in how many ways can he select a sample so that at least one of the chips is defective?

Assume that the chips are distinguishable

The total number of sets possible = C(13,2) = 78

The total number of sets which contain no defective chips = C(10,2) = 45

So.....the number of sets containing at least 1 defective chip = 78 - 45 = 33