A bag of marbles contains 7 blue, 7 green, 8 red, 9 yellow, and 3 black marbles. If you reach in the bag and draw one marble at random, what is the probability that you will draw a yellow marble?

How many yellows are there? How many marbles total?

Then, \text{probability drawing yellow=}\frac{\text{number of yellows}}{\text{number total}}