2. Вычислите: $$4\frac{1}{2} - (6-3\frac{7}{9}) : \frac{4}{5} - \frac{5}{6}$$.
Решение:
- $$6 - 3\frac{7}{9} = 5\frac{9}{9} - 3\frac{7}{9} = 2\frac{2}{9} = \frac{2 \cdot 9 + 2}{9} = \frac{20}{9}$$
- $$\frac{20}{9} : \frac{4}{5} = \frac{20}{9} \cdot \frac{5}{4} = \frac{20 \cdot 5}{9 \cdot 4} = \frac{5 \cdot 5}{9 \cdot 1} = \frac{25}{9} = 2\frac{7}{9}$$
- $$4\frac{1}{2} - 2\frac{7}{9} = 4\frac{9}{18} - 2\frac{14}{18} = 3\frac{27}{18} - 2\frac{14}{18} = 1\frac{13}{18}$$
- $$1\frac{13}{18} - \frac{5}{6} = 1\frac{13}{18} - \frac{5 \cdot 3}{6 \cdot 3} = 1\frac{13}{18} - \frac{15}{18} = \frac{31}{18} - \frac{15}{18} = \frac{16}{18} = \frac{8}{9}$$
Ответ: $$\frac{8}{9}$$