\[\frac{a - 5b}{b} = 8.\ \]
\[\frac{a - 5b}{b} = 8\]
\[a - 5b = 8b\]
\[a = 13b\]
\[\frac{3a - b}{a} = \frac{3 \cdot 13b - b}{13b} = \frac{39b - b}{13b} =\]
\[= \frac{38b}{13b} = \frac{38}{13} = 2\frac{12}{13}.\]