AHSME 1951 Problem 2

A rectangular field is half as wide as it is long and is completely enclosed by $x$ yards of fencing. The area in terms of $x$ is: $(\mathrm{A})\ \frac{x^2}2 (\mathrm{B})\ 2x^2 (\mathrm{C})\ \frac{2x^2}9 (\mathrm{D})\ \frac{x^2}{18} (\mathrm{E})\ \frac{x^2}{72}$