You may have missed the word monthly and used $\displaystyle{m}={1}\usepackage{cmbright}\Huge\$ . You should be using $\displaystyle{m}={12}\usepackage{cmbright}\Huge\$ , along with $\displaystyle{P}={10},{000}\usepackage{cmbright}\Huge\$ , $\displaystyle{r}={0.03}\usepackage{cmbright}\Huge\$ , and $\displaystyle{t}={10}\usepackage{cmbright}\Huge\$ . Substitute into the formula and simplify.