When you found the perimeter, you may have included the small length that separates the polygon into a triangle and a square. However, this is not part of the boundary of the polygon. When you found the 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.