8) 1/(13/20 - 18/27)

Давай решим примеры. Для удобства переведем всё в обыкновенные или десятичные дроби. **8)** $\frac{1}{\frac{13}{20} - \frac{18}{27}} = \frac{1}{\frac{13}{20} - \frac{2}{3}} = \frac{1}{\frac{39-40}{60}} = \frac{1}{-\frac{1}{60}} = -60$ **9)** $\frac{1}{\frac{17}{28} + \frac{7}{12}} = \frac{1}{\frac{51+49}{84}} = \frac{1}{\frac{100}{84}} = \frac{84}{100} = 0,84$ **10)** $(8\frac{1}{2} + \frac{4}{5}) \cdot 8 = (8,5 + 0,8) \cdot 8 = 9,3 \cdot 8 = 74,4$ **11)** $(3\frac{14}{15} - 1\frac{3}{9}) \cdot 9 = (3\frac{14}{15} - 1\frac{1}{3}) \cdot 9 = (3\frac{14}{15} - 1\frac{5}{15}) \cdot 9 = 2\frac{9}{15} \cdot 9 = 2\frac{3}{5} \cdot 9 = 2,6 \cdot 9 = 23,4$ **12)** $3\frac{9}{14} : (9\frac{6}{7} + 2\frac{6}{21}) = \frac{51}{14} : (9\frac{18}{21} + 2\frac{6}{21}) = \frac{51}{14} : 11\frac{24}{21} = \frac{51}{14} : 12\frac{3}{21} = \frac{51}{14} : 12\frac{1}{7} = \frac{51}{14} : \frac{85}{7} = \frac{51}{14} \cdot \frac{7}{85} = \frac{3}{2} \cdot \frac{1}{5} = \frac{3}{10} = 0,3$ **13)** $2\frac{10}{21} : (2\frac{11}{14} - 1\frac{25}{30}) = \frac{52}{21} : (2\frac{11}{14} - 1\frac{5}{6}) = \frac{52}{21} : (2\frac{33}{42} - 1\frac{35}{42}) = \frac{52}{21} : (1\frac{75}{42} - 1\frac{35}{42}) = \frac{52}{21} : \frac{40}{42} = \frac{52}{21} : \frac{20}{21} = \frac{52}{21} \cdot \frac{21}{20} = \frac{52}{20} = 2,6$ **22)** $\frac{5,4}{12 - \frac{3}{19}} = \frac{5,4}{\frac{228-3}{19}} = \frac{5,4}{\frac{225}{19}} = 5,4 \cdot \frac{19}{225} = \frac{54}{10} \cdot \frac{19}{225} = \frac{27}{5} \cdot \frac{19}{225} = \frac{3 \cdot 19}{5 \cdot 25} = \frac{57}{125} = 0,456$ **23)** $10\frac{1}{2} \cdot 4,92 + 4,03 : \frac{1}{7} = 10,5 \cdot 4,92 + 4,03 \cdot 7 = 51,66 + 28,21 = 79,87$ **24)** $2\frac{8}{12} : 0,04 + 75,7 \cdot 3\frac{10}{12} = 2\frac{2}{3} : \frac{4}{100} + 75,7 \cdot 3\frac{5}{6} = \frac{8}{3} \cdot 25 + 75,7 \cdot \frac{23}{6} = \frac{200}{3} + \frac{1741,1}{6} = 66,666... + 290,1833... = 356,85$ **25)** $1\frac{3}{12} \cdot 88,8 - 3,39 : \frac{2}{4} = 1,25 \cdot 88,8 - 3,39 : 0,5 = 111 - 6,78 = 104,22$ **26)** $(10\frac{1}{4} - 0,207) : \frac{1}{12} + 14 \cdot 3\frac{3}{7} = (10,25 - 0,207) \cdot 12 + 14 \cdot \frac{24}{7} = 10,043 \cdot 12 + 2 \cdot 24 = 120,516 + 48 = 168,516$ **27)** $(\frac{10}{12} + 0,493) : 7\frac{4}{6} - 3,23 \cdot 2\frac{8}{10} = (0,833... + 0,493) : 7\frac{2}{3} - 3,23 \cdot 2,8 = 1,3266... : \frac{23}{3} - 9,044 = 0,1732... \cdot 3 - 9,044 = 0,5197... - 9,044 = -8,5242...$ *(Примечание: в №27 результат дробный, перепроверь условие на опечатки в числах)*