Answer
<em>length = width + 15</em>
<em>Area = length * width; area is 54 square feet.</em>
<em>Two equations are:</em>
<em>L = W + 15</em>
<em>L * W = 54</em>
<em>To solve, we substitute first equation into second equation:</em>
<em>(W + 15) * W = 54</em>
<em>w^2 + 15w = 54</em>
<em>w^2 + 15w - 54 = 0</em>
<em>(w+18)(w-3) = 0</em>
<em>w = -18 or 3</em>
<em>The width cannot be negative, so 3 is the width and since length is 15 more than width, length is 18:</em>
<em />
<em>Length = 18 feet</em>
<em>Width = 3 feet</em>
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