Question 437083
Assuming the parking lot is a rectangle, which is key, we know that:
Perimeter = 2*Length + 2*Width
P = 2L + 2W
P = 2(L+W)
.
We're told that 
P = 500
So,
2(L+W) = 500
L+W = 250
.
And we're told:
L = W+20
.
Substituting, we have:
L+W = 250
(W+20) + W = 250
2W = 230
W = 115
.
So,
L = 250 -115
L = 135
.
The parking lot has dimensions:  Length = 135 and Width = 115.
.
Done.