\[\boxed{\mathbf{1168\ (1160)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ 4ax = 84\]
\[x = - 3:\ \ \ \]
\[4a \cdot ( - 3) = 84\]
\[- 12a = 84\]
\[a = - 7\]
\[Ответ:при\ a = - 7.\]
\[2)\ (a - 7)x = 6 + 5a\]
\[x = 1:\]
\[(a - 7) \cdot 1 = 6 + 5a\]
\[a - 7 = 6 + 5a\]
\[5a - a = - 7 - 6\]
\[4a = - 13\]
\[a = - 3,25\]
\[Ответ:при\ a = - 3,25.\]