#### Answer

A = $\frac{x^{2}}{2}$

#### Work Step by Step

The length is twice the width so
$2 \times Width$ = length
Width = $\frac{length}{2}$
The length is given as $x$ so
Width = $\frac{x}{2}$
Since the area $A$ of a rectangle is length times width, then
A = ($\frac{x}{2}$)($x$)
A = $\frac{x^{2}}{2}$