3. a) Вычислите: $$\frac{21}{22} - \frac{2}{19} : \frac{44}{57}$$.

Выполним вычисления: $$\frac{21}{22} - \frac{2}{19} : \frac{44}{57} = \frac{21}{22} - \frac{2}{19} * \frac{57}{44} = \frac{21}{22} - \frac{2}{19} * \frac{3 * 19}{44} = \frac{21}{22} - \frac{2 * 3}{44} = \frac{21}{22} - \frac{6}{44} = \frac{21}{22} - \frac{3}{22} = \frac{18}{22} = \frac{9}{11}$$ Ответ: $$\frac{9}{11}$$