You have put the decimal point in the wrong place. Notice that 100 is a multiple of 50. Multiply $\displaystyle\frac{{7}}{{50}}\usepackage{cmbright}\Huge\$ by $\displaystyle\frac{{2}}{{2}}\usepackage{cmbright}\Huge\$ to get $\displaystyle\frac{{14}}{{100}}\usepackage{cmbright}\Huge\$ . Now convert to a decimal and a percent.