\[\boxed{\text{971\ (971).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[- 12x + 17y = - 87;\ x = - y\]
\[12y + 17y = - 87\]
\[29y = - 87\]
\[y = - 3 \Longrightarrow \ \ (3;\ - 3)\]
\[Ответ:(3;\ - 3).\]