\[\boxed{\text{1263.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ y = 2 - 3x;\ \ 2x + 3y = 7\]
\[\left\{ \begin{matrix} 3x + y = 2\ \ \ | \cdot ( - 3) \\ 2x + 3y = 7\ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]
\[\left\{ \begin{matrix} - 9x - 3y = - 6 \\ 2x + 3y = 7\ \ \ \ \ \ \\ \end{matrix} \right.\ ( + )\]
\[- 7x = 1\]
\[x = - \frac{1}{7};\]
\[y = 2 - 3x = 2 - 3 \cdot \left( - \frac{1}{7} \right) =\]
\[= 2 + \frac{3}{7} = 2\frac{3}{7}.\]
\[Ответ:\left( - \frac{1}{7};\ \ 2\frac{3}{7} \right).\]
\[2)\ 5x + 6y = - 20;\ \ 2x + 9y = 25\]
\[\left\{ \begin{matrix} 5x + 6y = - 20\ \ | \cdot ( - 2) \\ 2x + 9y = 25\ \ \ \ \ \ | \cdot 5\ \ \ \ \ \ \ \\ \end{matrix} \right.\ \]
\[\left\{ \begin{matrix} - 10x - 15y = 40 \\ 10x + 45y = 125 \\ \end{matrix} \right.\ ( + )\]
\[30y = 165\]
\[y = \frac{165}{30} = \frac{11}{2} = 4,5;\]
\[2x = 25 - 9y = 25 - 40,5 = - 14,5\]
\[x = - 7,25.\]
\[Ответ:( - 7,25;4,5).\]