Question 282655
Width = W
Length = 3W
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{{{ (3W+3)(W-1) = 72 }}}

Expand to:
{{{ 3W^2 + 3W - 3W - 3 = 72 }}}

Simplify and add 3 to each side:
{{{ 3W^2 - 3 + 3 = 72 + 3 }}}

{{{ 3W^2 = 75 }}}

Divide each side by 3:
{{{ (3W^2)/3 = 75/3 }}}

Take the square root of each side:
{{{ W^2 = 25 }}}

{{{ W = 5 }}} & bobs your uncle!