Divide both sides by $\displaystyle{R}{T}\usepackage{cmbright}\Huge\$ : $\displaystyle\frac{{{P}{V}}}{{{R}{T}}}=\frac{{{n}{R}{T}}}{{{R}{T}}}\usepackage{cmbright}\Huge\$

Simplify to: $\displaystyle\frac{{{P}{V}}}{{{R}{T}}}={n}\usepackage{cmbright}\Huge\$