Probability question

$6 \over 19$ chance for the first marble

$5 \over 19$ chance for the second marble

$8 \over 19$ chance for the third marble. 

Because they all "rely" on each other, the probability is the product of all 3 cases. 

Good try Builderboi, but not quite right.

8/19 * 7/18 * 6/17 =

OR

8C3 /  19C3  =   

this is two different ways to do it, the answer is the same each time.