To solve this problem you must use the formula of the perimeter (P) of a rectangle and clear the length (L). The perimeter of a rectangle, is:
P=2L+2W
"P" is the perimeter of the rectangle (P=180 feet).
"L" is the lenght of the rectangle.
"W" is the widht of the rectangle (W=30 1/4 feet=30.25 feet).
As you can see, you already have the value of the perimeter (P) and the value of the widht (W). Now, you can clear the lenght (L):
P=2L+2W
2L=P-2W
L=(P-2W)/2
When you substitute the values, you obtain:
L=(P-2W)/2
L=(180 feet-2x30.25 feet)/2
L=(119.5 feet)/2
L=59.75 feet
What must the length be?
The answer is: 59.75 feet