After substitution you will have $\displaystyle{\left({3}\cdot{\left(-\frac{{1}}{{5}}\right)}\right)}\cdot{5}={3}\cdot{\left({\left(-\frac{{1}}{{5}}\right)}\cdot{5}\right)}={3}\cdot{\left(-\frac{{5}}{{5}}\right)}={3}\cdot{\left(-{1}\right)}\usepackage{cmbright}\Huge\$