\[\boxed{\text{158\ (158).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ 2 + 4x = m - 6\]
\[4x = m - 8\]
\[x = \frac{m - 8}{4}\]
\[\frac{m - 8}{4} \geq 0\]
\[m - 8 \geq 0\]
\[m \geq 8\]
\[Ответ:при\ m \in \lbrack 8;\ + \infty).\]
\[2)\ mx = m^{2} - 7m\]
\[x = \frac{m^{2} - 7m}{m}\]
\[x = \frac{m(m - 7)}{m}\]
\[x = m - 7,\ \ m \neq 0\ \]
\[m - 7 < 0\]
\[m < 7\]
\[Ответ:при\ m \in ( - \infty;7);\ \]
\[кроме\ 0.\]
\[\boxed{\text{158.\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[5x - y = 2;\ \ A\ (4;b):\]
\[5 \cdot 4 - y = 2\]
\[20 - 2 = y\]
\[18 = y\]
\[b = 18\]
\[Ответ:b = 18.\]