\[При\ x = 17:\]
\[41 - (a + x) = 16\]
\[41 - (a + 17) = 16\]
\[a + 17 = 41 - 16\]
\[a + 17 = 25\]
\[a = 25 - 17\]
\[a = 8.\]
\[Ответ:нужно\ подставить\ a = 8.\ \]