Вычислите: 7/9 - 5/6 + 4/15; (2/3 - 4/9) * 3/8; 2/7 + 3/8 : 7/32; 5/9 : (7/9 + 11/18)

1. $\frac{7}{9} - \frac{5}{6} + \frac{4}{15} = \frac{7 \cdot 10 - 5 \cdot 15 + 4 \cdot 6}{90} = \frac{70 - 75 + 24}{90} = \frac{19}{90}$ **Ответ: 19/90** 2. $(\frac{2}{3} - \frac{4}{9}) \cdot \frac{3}{8} = (\frac{6 - 4}{9}) \cdot \frac{3}{8} = \frac{2}{9} \cdot \frac{3}{8} = \frac{2 \cdot 3}{9 \cdot 8} = \frac{1}{3 \cdot 4} = \frac{1}{12}$ **Ответ: 1/12** 3. $\frac{2}{7} + \frac{3}{8} : \frac{7}{32} = \frac{2}{7} + \frac{3}{8} \cdot \frac{32}{7} = \frac{2}{7} + \frac{3 \cdot 4}{1 \cdot 7} = \frac{2}{7} + \frac{12}{7} = \frac{14}{7} = 2$ **Ответ: 2** 4. $\frac{5}{9} : (\frac{7}{9} + \frac{11}{18}) = \frac{5}{9} : (\frac{14 + 11}{18}) = \frac{5}{9} : \frac{25}{18} = \frac{5}{9} \cdot \frac{18}{25} = \frac{1 \cdot 2}{1 \cdot 5} = \frac{2}{5}$ **Ответ: 2/5**