Решите систему уравнений: 2(3a-4b)-4(b+5)=4; 3(8b-5)-(7-2a)=-42.

\[\left\{ \begin{matrix}
2(3a - 4b) - 4(b + 5) = 4\ \ \ \\
3(8b - 5) - (7 - 2a) = - 42 \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix}
6a - 8b - 4b - 20 = 4\ \ \ \ \ \\
24b - 15 - 7 + 2a = - 42 \\
\end{matrix} \right.\ \]

\[\left\{ \begin{matrix}
6a - 12b = 24\ \ \ \ | \cdot 2 \\
2a + 24b = - 20\ \ \ \ \ \ \ \ \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix}
12a - 24b = 48\ \\
2a + 24b = - 20 \\
\end{matrix} \right.\ + \ \ \ \ \]

\[\left\{ \begin{matrix}
14a = 28\ \ \ \ \ \ \ \\
b = \frac{12a - 48}{24} \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix}
a = 2\ \ \ \\
b = - 1 \\
\end{matrix} \right.\ \]

\[Ответ:(2;\ - 1).\]