A bag contains only green, yellow and red marbles. The ratio of green marbles to yellow marbles to red marbles in the bag is $3: 4: 2$. If 63 of the marbles in the bag are not red, the number of red marbles in the bag is
(A) 14
(B) 18
(C) 27
(D) 36
(E) 81
Since the ratio of green marbles to yellow marbles to red marbles is $3: 4: 2$, then we can let the numbers of green, yellow and red marbles be $3 n, 4 n$ and $2 n$ for some positive integer $n$. Since 63 of the marbles in the bag are not red, then the sum of the number of green marbles and the number of yellow marbles in the bag is 63 .

Thus, $3 n+4 n=63$ and so $7 n=63$ or $n=9$, which means that the number of red marbles in the bag is $2 n=2 \times 9=18$.

ANSwER: (B)