Вычисли первое выражение: 7/9 - 5/6 + 4/15

1. $\frac{7}{9} - \frac{5}{6} + \frac{4}{15} = \frac{7*10 - 5*15 + 4*6}{90} = \frac{70 - 75 + 24}{90} = \frac{19}{90}$ 2. $(2\frac{4}{9}) \cdot (\frac{3}{8}) = (\frac{2*9+4}{9}) \cdot (\frac{3}{8}) = \frac{22}{9} \cdot \frac{3}{8} = \frac{11}{3} \cdot \frac{1}{4} = \frac{11}{12}$ 3. $2\frac{3}{7} + \frac{7}{8} : \frac{32}{7} = \frac{2*7+3}{7} + \frac{7}{8} \cdot \frac{7}{32} = \frac{17}{7} + \frac{49}{256} = \frac{17*256 + 49*7}{7*256} = \frac{4352 + 343}{1792} = \frac{4695}{1792} = 2\frac{1111}{1792}$ 4. $\frac{5}{9} : (\frac{7}{9} + \frac{11}{18}) = \frac{5}{9} : (\frac{7*2 + 11}{18}) = \frac{5}{9} : \frac{25}{18} = \frac{5}{9} \cdot \frac{18}{25} = \frac{1}{1} \cdot \frac{2}{5} = \frac{2}{5}$ 5. $1 - \frac{4}{7} : \frac{16}{21} = 1 - \frac{4}{7} \cdot \frac{21}{16} = 1 - \frac{1}{1} \cdot \frac{3}{4} = 1 - \frac{3}{4} = \frac{1}{4}$ 6. $\frac{5}{12} : (\frac{1}{3} + \frac{5}{25}) = \frac{5}{12} : (\frac{1}{3} + \frac{1}{5}) = \frac{5}{12} : (\frac{5 + 3}{15}) = \frac{5}{12} : \frac{8}{15} = \frac{5}{12} \cdot \frac{15}{8} = \frac{5}{4} \cdot \frac{5}{8} = \frac{25}{32}$ 7. $39 : (\frac{1}{7} + \frac{6}{49}) = 39 : (\frac{7 + 6}{49}) = 39 : \frac{13}{49} = 39 \cdot \frac{49}{13} = 3 \cdot 49 = 147$ 8. $\frac{9}{14} : (\frac{17}{24} - \frac{5}{12}) = \frac{9}{14} : (\frac{17 - 5*2}{24}) = \frac{9}{14} : (\frac{17 - 10}{24}) = \frac{9}{14} : \frac{7}{24} = \frac{9}{14} \cdot \frac{24}{7} = \frac{9}{7} \cdot \frac{12}{7} = \frac{108}{49} = 2\frac{10}{49}$ 9. $16 \frac{3}{5} + (\frac{4}{8}) = \frac{16*5 + 3}{5} + \frac{1}{2} = \frac{83}{5} + \frac{1}{2} = \frac{83*2 + 1*5}{10} = \frac{166 + 5}{10} = \frac{171}{10} = 17\frac{1}{10}$ 10. $35 : (\frac{8}{6} + \frac{5}{12}) = 35 : (\frac{8*2 + 5}{12}) = 35 : (\frac{16 + 5}{12}) = 35 : \frac{21}{12} = 35 \cdot \frac{12}{21} = 5 \cdot \frac{12}{3} = 5 \cdot 4 = 20$