Question 691394
Nearly correct !

Let length={{{ x }}}, then width={{{x-7}}}

Area = 250 so {{{ x (x-7) = 250 }}}, Expanding gives:
{{{ x^2 - 7x = 250 }}}
{{{ x^2 - 7x - 250 = 0 }}}
Solving using the quadratic formula gives:
{{{x = (7 +- sqrt( 49+1000 ))/(2) }}}
{{{x = -12.69 }}} or {{{x = 19.69 }}} (working to 2dp)
Obviously as x is the length then {{{x >0 }}} so solution is {{{x = 19.69 }}}