\[\boxed{\text{957\ (957).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ x + y = 12\]
\[x = 12 - y\ \]
\[(1;11),\ (0;12),\ (15;\ - 3).\]
\[2)\ x - 7y = 5\ \ \]
\[x = 5 + 7y\ \]
\[(12;1),\ (5;0),\ (19;2).\]
\[3)\ 2x + 8y = 16\ \ \ |\ \ :2\]
\[x + 4y = 8\ \ \]
\[x = 8 - 4y\]
\[(8;0),\ (4;1),\ (12;\ - 1)\]
\[4) - 6x + 5y = 18,\ \ \]
\[- 6x = 18 - 5y\ \]
\[6x = 5y - 18\]
\[x = \frac{5}{6}y - 3\]
\[( - 3;0),\ (7;12),\ (2;6).\]