Решите систему уравнений: 2(3x+2y)+9=4x+21; 2x+10=3-(6x+5y).

\[\left\{ \begin{matrix} 2(3x + 2y) + 9 = 4x + 21 \\ 2x + 10 = 3 - (6x + 5y)\text{\ \ \ } \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} 6x + 4y + 9 = 4x + 21 \\ 2x + 10 = 3 - 6x - 5y \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} 2x + 4y = 12\ \ \ | \cdot 4 \\ 8x + 5y = - 7\ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} 8x + 16y = 48 \\ 8x + 5y = - 7\ \ \\ \end{matrix} \right.\ ( - )\]

\[11y = 55\]

\(y = 5;\ \)

\[2x = 12 - 4y = 12 - 20 = - 8\]

\[x = - 4.\]

\[Ответ:( - 4;5).\]