\[\frac{a - 3b}{b} = 4\]
\[\frac{a}{b} - \frac{3b}{b} = 4\]
\[\frac{a}{b} - 3 = 4\]
\[\frac{a}{b} = 4 + 3 = 7\]
\[\frac{a}{b} = 7.\]