\[\left\{ \begin{matrix} p - 3q = 5\ \ | \cdot ( - 3) \\ 3p + 2q = 4\ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} - 3p + 9q = - 15\ \ (1) \\ 3p + 2q = 4\ \ \ \ \ \ \ \ \ \ \ (2) \\ \end{matrix} \right.\ \]
\[(1) + (2) \Longrightarrow 11q = - 11\]
\[\left\{ \begin{matrix} 11q = - 11 \\ p - 3q = 5 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} 11q = - 11 \\ p = 5 + 3q \\ \end{matrix} \right.\ \]