You found the correct perimeter of the polygon, but not the correct area. You may have forgotten the $\displaystyle\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ in the area formula for a triangle. The correct answer is $\displaystyle{P}={30}\usepackage{cmbright}\Huge\$ meters, $\displaystyle{A}={42}\usepackage{cmbright}\Huge\$ square meters.