**a)**
\(\frac{3}{6} \cdot \frac{4}{6} = \frac{3 \cdot 4}{6 \cdot 6} = \frac{12}{36}\)
Сокращаем дробь \(\frac{12}{36}\) на 12:
\(\frac{12}{36} = \frac{1}{3}\)
**b)**
\(\frac{2}{6} : \frac{8}{3} = \frac{2}{6} \cdot \frac{3}{8} = \frac{2 \cdot 3}{6 \cdot 8} = \frac{6}{48}\)
Сокращаем дробь \(\frac{6}{48}\) на 6:
\(\frac{6}{48} = \frac{1}{8}\)
**Ответ:**
a) \(\frac{1}{3}\)
b) \(\frac{1}{8}\)