Question 279061
{{{A = Area of rectangle}}} 
{{{L = Length}}}
{{{W = Width}}}
{{{A = L * W}}}
{{{A = 108}}}
{{{L = 3W}}}
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{{{108 = L * W = 3W * W = 3W^2}}}
{{{W^2 = 108/3 = 36}}}
{{{W = sqrt(36) =  6}}}
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The square root of 36 is either +6 or -6, BUT a negative width does not make sense, so we can start with w=6.
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{{{L = 3W = 3*6 = 18}}}
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Checking the A
{{{18 * 6 = 108}}}
OK.
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Answer:
The rectangle's length is 18; the width is 6.
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Done