Question 866405
Let A=area
Let w = width
Let L = length
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Description is, {{{w=L+6}}}.
{{{wL=A}}}
{{{(L+6)L=A}}}
{{{A=L^2+6}}}
This is really all that can be done unless you have further information.  You only have enough information to make a formula for A in terms of w or A in terms of L; if you solve the described information for L and then substitute for L instead.