A bag has 9 red marbles, 6 blue marbles, and 5 yellow marbles. What is the probability of NOT choosing a yellow marble from the bag?

Answer 1

If you determine what the probability of CHOOSING a yellow marble then you can just subtract it from 1 to get the probability of NOT choosing yellow.

There are 20 marbles total and there are 5 yellow so the probability of choosing yellow is 5/20. Therefore the probability of NOT choosing yellow is 1 - 5/20 = 20/20 - 5/20 = 15/20 = 3/4