Remember to multiply both the numerator and denominator by the same number. When you multiply the numerator and denominator of $\displaystyle\frac{{3}}{{15}}\usepackage{cmbright}\Huge\$ by 3, you are left with the fraction $\displaystyle\frac{{9}}{{45}}\usepackage{cmbright}\Huge\$ , which is not equivalent to $\displaystyle\frac{{3}}{{45}}\usepackage{cmbright}\Huge\$ . The correct answer is $\displaystyle\frac{{10}}{{18}}\usepackage{cmbright}\Huge\$ and $\displaystyle\frac{{15}}{{27}}\usepackage{cmbright}\Huge\$ .