A bag contains yellow, green, blue, and white marbles in the ratio 4:2:3:7. If the bag contains 240 marbles, then how many blue marbles are there?
3 / (4 + 2 + 3 + 7) * 240 =
(3 / 16) * 240 =
3 * (240 / 16) =
3 * 15 =
45 blue
+1911 
