\(\frac{12}{9} = \frac{4 \cdot 3}{3 \cdot 3} = \frac{4}{3}\)
\(\frac{c}{c} \cdot \frac{b^2}{b^3} = 1 \cdot \frac{1}{b} = \frac{1}{b}\)
\(\frac{4}{3} \cdot \frac{1}{b} = \frac{4}{3b}\)
Ответ: \(\frac{4}{3b}\)