probabilty problem explained in simple terms

Question

Help me how to solve and explain this probability problem in simple terms.

In a bag there are 20 balls, 12 green balls, and 8 white balls.

You draw three balls at random.

If you get 3 white balls, you win $5, if you draw 3 green balls you lose $1, otherwise you neither win nor lose.

You can draw the balls in two ways:

1. draw with replacement, or
2. draw without replacement.

Which way you should choose to draw so as to maximize winning? Explain why.

Answer 1

Pr(3W) = 8/20 x 7/19 x 6/18= about 4.9%, if without replacement

Pr(3W) = 8/20 x 8/20 x 8/20 = (4/10)^3 = 6.4%, if with replacement

only replace if you select a white ball

if you get a green, do not replace it