\[\frac{5x + 1}{8} = \frac{1}{3}\]
\[3(5x + 1) = 8\]
\[15x + 3 = 8\]
\[15x = 5\]
\[x = \frac{5}{15} = \frac{1}{3}.\]
\[Ответ:x = \frac{1}{3}.\]