Question 792408
length = w + 5
A = lw
84 = (w + 5)w
84 = w^2 + 5w
y = w^2 + 5w -84
(w - 7)(w + 12)
w - 7 = 0
w - 7 + 7 = 7
w = 7

w + 12 = 0
w + 12 - 12 = -12
w = -12

w = 7 is correct, you can not have a negative value for the dimension.



check:
84 = (7 + 5)7
84 = (12)7
84 = 84