Nathaniel had a bag of 5 green marbles, 3 blue marbles, 6 red marbles, and 6 yellow marbles. Find the probability if Nathaniel pulls a blue marble doesn't replace it and then pulls another blue marbel.

To find probability, you'd have to find the total number of marbles (5+3+6+6=20), and since there are 3 blue marbles, the probability of picking one is 3 out of 20, or 3/20

If that blue marble isn't replaced, there will then be 19 marbles, and 2 blue ones. So the probability of him picking another blue marble is 2/19