8
A = L * W, W = L - 7
120 = L * (L - 7)
L^2 - 7L - 120 = 0
(L - 15)(L + 8) = 0
Use only the positive value which is L - 15.
L - 15 = 0
L = 15 inches
Solve for W:
W = L - 7
W = 15 - 7
W = 8 inches
Now lets check:
L * W = 120
15 * 8 = 120
120 = 120 (the values are correct)
L = 15 inches, W = 8 inches
Added 7/20/2020 2:16:15 PM
This answer has been confirmed as correct and helpful.