19. \(\frac{18}{49}\cdot\frac{21}{27}=\)

Сократим: \(\frac{18}{27}=\frac{2}{3}\), \(\frac{21}{49}=\frac{3}{7}\).

\(\frac{18}{49}\cdot\frac{21}{27}=\frac{2}{3}\cdot\frac{3}{7}=\frac{2}{7}\).

Ответ: \(\frac{2}{7}\)