At least a third of Fred's marbles are dark blue. All of the rest are red, except for 4 that are green. If he has 63 marbles, how many of them are red?
Fred has 63/3 = <T>divide(63, 3)=21.0 dark blue marbles.
Fred has 63-21 = <T>subtract(63, 21)=42 red and green marbles.
Fred has 42-4 = <T>subtract(42, 4)=38 red marbles.
