Answer
The length is 15.7 ft and the width is 9.8 ft.
Work Step by Step
P is the perimeter, l is the length, and w is the width.
$P=51=2w+2l$, and $l=w+5.9$
Substitute.
$51=2w+2(w+5.9)$
Distribute.
$51=2w+2w=11.8$
Combine like terms.
$51=4w+11.8$
Subtract 11.8 from both sides.
$39.2=4w$
Divide both sides by 4.
$9.8=w$
Substitute the value of w to find the length.
$l=(9.8)+5.9$
Add.
$l=15.7$
Check.
$2(15.7)+2(9.8)=51$