1. \(\frac{11}{12}\cdot\frac{21}{22}=\)

Сократим множители 11 и 22:

\(\frac{11}{12}\cdot\frac{21}{22}=\frac{1}{12}\cdot\frac{21}{2}=\frac{21}{24}=\frac{7}{8}\).

Ответ: \(\frac{7}{8}\).