\[\left\{ \begin{matrix} 3x - by = 12 \\ ax + 2y = 14 \\ \end{matrix} \right.\ \]
\[\left\{ \begin{matrix} - 6 - 3b = 12 \\ - 2a + 6 = 14 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} - 3b = 18 \\ - 2a = 8 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} b = - 6 \\ a = - 4 \\ \end{matrix} \right.\ \]
\[Ответ:a = - 4;\ \ b = - 6.\]