#### Answer

$C$

#### Work Step by Step

The formula for the perimeter of a rectangle is given by the following formula:
$P = 2l + 2w$
Let's define our variables:
$w$ = width
$l$ = $2w$
Let's substitute $2w$ into the equation and plug in $72$ for $P$:
$72 = 2(2w) + 2w$
Multiply first:
$4w + 2w = 72$
Add the left side to simplify:
$6w = 72$
Divide each side by $6$ to solve for $w$:
$w = 12$
We want to find length, so we plug in $w$ in our expression for $l$ to find length:
$l = 2(12)$
Multiply to solve for $l$:
$l = 24$ in.
The answer is option $C$.