You probably set up the ratio incorrectly, equating $\displaystyle{{\sin{{39}}}}^{\circ}\usepackage{cmbright}\Huge\$ with $\displaystyle\frac{{10}}{{y}}\usepackage{cmbright}\Huge\$ . A correct way to set up the equation is $\displaystyle{{\sin{{39}}}}^{\circ}=\frac{{y}}{{10}}\usepackage{cmbright}\Huge\$ . Solve this equation for y and round off.