\[\boxed{\mathbf{923\ (923)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[\textbf{а)}\ x + 21 = 7\]
\[x = 7 - 21\]
\[x = - (21 - 7)\]
\[x = - 14.\]
\[Ответ:x = - 14.\]
\[\textbf{б)}\ 32 + x = - 25\]
\[x = - 25 - 32\]
\[x = - (25 + 32)\]
\[x = - 57.\]
\[Ответ:x = - 57.\]
\[\textbf{в)}\ x + 12,5 = - 7,5\]
\[x = - 7,5 - 12,5\]
\[x = - (7,5 + 12,5)\]
\[x = - 20.\]
\[Ответ:x = - 20.\]
\[\textbf{г)}\ 15,2 + x = 2,3\]
\[x = 2,3 - 15,2\]
\[x = - (15,2 - 2,3)\]
\[x = - 12,9.\ \]
\[Ответ:\ \ x = - 12,9.\]