Question 942344
The formula for area is:
{{{ A = L*W }}}
{{{ L = 2W + 4 }}} ft
{{{ A = 160 }}} ft2
------------------
by substitution:
{{{ 160 = ( 2W + 4 )*W }}}
{{{ 160 = 2W^2 + 4W }}}
{{{ W^2 + 2W - 80 }}}
{{{ ( W + 10 )*( W - 8 ) }}}
{{{ W = 8 }}} ( can only use the positive solution )
and
{{{ L = 2W + 4 }}} 
{{{ L = 2*8 + 4 }}}
{{{ L = 20 }}}
----------------
The length is 20 ft