#### Answer

c. length = 9 feet; width = 6 feet

#### Work Step by Step

Let $l$ be the length of the rectangle.
Let $w$ be the width of the rectangle.
Length is 3 feet longer than the width.
$l=w+3$
Perimeter is 30 feet.
$2l+2w=30$
$l=w+3$
$2l+2w=30$
$2(w+3)+2w=30$
$2w+6+2w=30$
$4w+6=30$
$4w=24$
$w=6$
$l=w+3$
$l=(6)+3$
$l=9$
Length is 9 feet and width is 6 feet, so the answer is c.