Answer: Found it by web and solving
Step-by-step explanation: L = W + 4
LW = 60
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LW = 60
(W + 4)W = 60
W^2 + 4W + (-60) = 0
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above is in quadratic equation form: ax^2 + bx + c = 0
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use the quadratic formula to solve for two solutions:
x = ( -b +- sqrt( bb - 4ac ) ) / 2a
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the two solutions are:
W = 6
W = -10
the negative solution doesn't make sense for length, so use the positive solution.
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L = 10
W = 6