Question 849962
{{{A[r]=L*W=30}}}
{{{W=L+7}}}
So,
{{{L*(L+7)=30}}}
{{{L^2+7L-30=0}}}
{{{(L+10)(L-3)=0}}}
Two solutions:
{{{L+10=0}}}
{{{L=-10}}}
Not a solution since negative length doesn't make sense.
{{{L-3=0}}}
{{{L=3}}}
then
{{{W=3+7=10}}}