There are $\frac{2}{3}$ as many golf balls in Bin $\mathrm{F}$ as in Bin G. If there are a total of 150 golf balls, how many fewer golf balls are in Bin F than in Bin G?
(A) 15
(B) 30
(C) 50
(D) 60
(E) 90
If the number of golf balls in Bin $\mathrm{G}$ is $x$, then the number of golf balls in Bin $\mathrm{F}$ is $\frac{2}{3} x$.

In this case, the total number of golf balls is $x+\frac{2}{3} x=\frac{3}{3} x+\frac{2}{3} x=\frac{5}{3} x$, and so $\frac{5}{3} x=150$.

Multiplying both sides of this equation by 3 , we get $5 x=150 \times 3=450$.

Dividing both sides by 5 , we get $x=\frac{450}{5}=90$ and so there are 90 golf balls in Bin G.

The number of golf balls in Bin F is $150-90=60$, and so there are $90-60=30$ fewer golf balls in Bin $\mathrm{F}$ than in Bin $\mathrm{G}$.

(Alternately, we may have begun by letting there be $3 x$ golf balls in Bin $\mathrm{G}$ and $2 x$ golf balls in Bin F.)

ANSWER: (B)