1. The problem statement, all variables and given/known data Given 9 good light bulbs and 4 defective light bulbs, how many ways can you select 3 such that you get exactly 1 defective bulb? 2. Relevant equations C(n,r) 3. The attempt at a solution I understand total ways to select is C(13,3)=286, and that total ways to select only good bulbs is C(9,3)=84. Subtracting these would give 202 ways to get 1 or more defective bulb. Not sure how to further differentiate these cases...answer provided is 144. If I just use rule of counting, I can pick from 4 bad, 9 good, then 8 bad in any order which is 288...double the provided answer.