Answer
$\mathrm{P}=\frac{R T}{M} \rho$
Work Step by Step
$\begin{array}{|l|l|}
\hline
{\text { PV = nRT }\quad\quad(1)} & {\text {Ideal Gas Equation.} }\\ \hline
{\text {$\mathrm{n}=\frac{m}{M}$} \quad\quad\quad\quad(2)} & {\text {Where : m is mass, M is Molar mass} }\\ \hline
{\text {$\mathrm{PV}=\frac{m}{M} \mathrm{RT}$} } & {\text {from (1), and (2)} }\\ \hline
{\text {$\rho=\frac{m}{V}$} } & {\text {The relation between mass, and density.} }\\ \hline
{\text {$\mathrm{P}=\frac{R T}{M} \rho$} } & {\text {From (3), and (4)} }\\ \hline
\end{array}$
