constraints:
x20; y20
y < -x +9

670 because there are 8 total marbles, which means that 7 out of the 8 marbles in the bag are not green.
so, the probability of not drawing a green marble is 7/8.
to draw 3 marbles that aren't green, you multiply 7/8 * 7/8 * 7/8 ,

which = .670. hope that !