Question 907629
For a rectangle,
{{{A=L*W}}}
{{{540=L*(L-12)}}}
{{{540=L^2-12L}}}
{{{L^2-12L-540=0}}}
{{{(L+18)(L-30)=0}}}
Two solutions but only one is positive.
{{{L-30=0}}}
{{{L=30}}}
Then,
{{{W=30-12}}}
{{{W=18}}}