Aparking lot that is 3 feet longer than it is wide has an area of 550 square feet. how many feet long is the parking lot?

Let W=width of parking lot,
then Length = W+3
Total area = W(W+3)=550
Exapand and express in standard quadratic form
W^2+3x-550=0
Factor
(W+25)(W-22)=0
Therefore W=22 or W=-25, reject negative root, so
Width = 22'
Length=22+3=25'
Check: (area = 22' * 25'=550 sq. ft, ok)

Check the picture below

bear in mind that, the length is 3 feet longer than the width

it cannot be -25.. since the length must not be a negative unit, just a length unit.