Answer:
15/4 in or 3.75 in
Step-by-step explanation:
Find your equations:
L = 4w + 9 in
A = L*w = 90 in^2
Substitute L:
L*w = 90 in^2 <-- L = 4w + 9
(4w + 9in)w = 90 in^2
4w^2 in^2 + 9w in = 90in^2
Solve Simultaneously:
w = -6 in, 15/4 in
Width is positive so it is 15/4 in or 3.75 in.
Double check:
(4w + 9in)w = 90 in^2
(4*3.75in + 9in)(3.75in) = 90 in^2
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