QR- DAT destroyer - Probability

[belmont3]

A jar contains 5 green marbles, 7 red marbles, and 3 blue marbles. Three marbles were drawn at random without replacement. What is the probability of drawing three red marbles?

a) 2/3
b) 1/3
c) 5/3
d) 1/7
e) 1/13

Can you please provide full solution with the answer?!
Thanks!

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[belmont3]

I believe the answer is E. I just did it really quick so my math might not be right. Multiply (7/15)(6/14)(5/13)... first draw there are 7 marbles and 15 total. Since there isn't replacement, both number will go down for the next replacement. Does that make sense?

Yes, Thanks a lot!!