17. \(\frac{11}{12}\cdot\frac{7}{12}\cdot\frac{21}{55}\)

Сократим: \(\frac{11}{55}=\frac{1}{5}\), \(\frac{21}{12}=\frac{7}{4}\).

Получаем \(\frac{7\cdot7}{12\cdot4\cdot5}=\frac{49}{240}\).

Ответ: \(\frac{49}{240}\)