You know that you need 3 of the same color, and every cycle will give you another one of the same color. If you want 3 of every color, you would need 30 gumballs. However, you only need 3 of 1 color, which means 2 of everything else. so 2x9 +3 = 21. 21 gumballs divided by 3 is 7 quarters, or $1.75.