\[3 \cdot (x - 1) = a - 8\]
\[x - 1 = \frac{a - 8}{3}\]
\[x = \frac{a - 8}{3} + 1^{\backslash 3} = \frac{a - 8 + 3}{3} = \frac{a - 5}{3}\]
\[Ответ:при\ a = 6.\]