Question 149381
Let {{{ A[old] = old Area }}}, with following conditions:
{{{L[length] = 3W+6 }}}
{{{ W[width] = W }}},
So, {{{ A[old] = L*W }}}----> {{{A[old] = (3W+6)(W)}}} 
{{{ A[old]= 3W^2 + 6W }}}
.
Let {{{ A[new] = new Area }}} with following conditions:
{{{ L[length] = 3W + 6 - 10 = 3W -4 }}}
{{{ W[width] = W+4 }}}
So, {{{ A[new] = L*W }}}----> {{{A[new] = (3W-4)(W+4)}}}
{{{ A[new] = 3W^2 + 8W -16 }}}
.
Equating the 2 Areas because of the conditions, becoming {{{A[old] = A[new]}}}
{{{ cross(3W^2) + 6W = cross(3W^2) + 8W -16 }}}, rearranging thereafter:
{{{ 8W - 6W =16 }}}----> {{{2W = 16}}}
{{{ W = 8 }}}
Going back to the old condition for {{{ L= 3W + 6}}}---> {{{L= (3*8)+6}}}
{{{ L= 30}}}
In doubt? Go back {{{A[old] = ((3*8)+6)(8)= 240}}}
Also, {{{A[new] = ((3*8)-4)(8+4)=240}}}
<font><font size=5><b> {{{A[old] = A[new]}}}</font>
Thank you,
Jojo