\[\boxed{\text{973\ (973).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[( - 4;2)\]
\[1)\ 3x + 5y = a\]
\[3 \cdot ( - 4) + 5 \cdot 2 = a\]
\[a = - 12 + 10 = - 2\]
\[Ответ:\ при\ a = - 2.\]
\[2)\ \text{ax} + 5y = 18\]
\[- 4a + 5 \cdot 2 = 18\]
\[- 4a = 8\]
\[a = - 2\]
\[Ответ:\ при\ a = - 2.\]