I need some help with the set up please.

Joella has a bag of marbles. The bag contains 10 red marbles, 5 green marbles, and 3 blue marbles. She will randomly select 2 marbles from the bag one at a time without replacement. What is the probability that Joella will select a red marble first and then a blue marble?

I got 10/18*3/16, but when I solve it, the answer is not one of the multiple choice answers. Thank you.

2 answers

try 10/18*3/17

how about 10/18 * 3/17 ??