You probably correctly substituted for l and solved for w. However, the length is 8 inches longer than the width, not the other way around. Always check your answer in the original equations. The left side of the second equation would be $\displaystyle{2}{\left({1}\right)}+{2}{\left({9}\right)}={2}+{18}={20}\usepackage{cmbright}\Huge\$ , not 52.