Пользуясь правилами сложения и вычитания дробей, выполните задания.

1. $\frac{5}{7} + \frac{2}{4} = \frac{5 \times 4 + 2 \times 7}{28} = \frac{20 + 14}{28} = \frac{34}{28} = \frac{17}{14} = 1\frac{3}{14}$ 2. $\frac{7}{15} - \frac{3}{10} = \frac{7 \times 2 - 3 \times 3}{30} = \frac{14 - 9}{30} = \frac{5}{30} = \frac{1}{6}$ 3. $\frac{11}{18} - \frac{4}{9} = \frac{11 - 4 \times 2}{18} = \frac{11 - 8}{18} = \frac{3}{18} = \frac{1}{6}$ 4. $\frac{13}{30} + \frac{14}{20} = \frac{13 \times 2 + 14 \times 3}{60} = \frac{26 + 42}{60} = \frac{68}{60} = \frac{17}{15} = 1\frac{2}{15}$ 5. $\frac{11}{16} - \frac{5}{12} = \frac{11 \times 3 - 5 \times 4}{48} = \frac{33 - 20}{48} = \frac{13}{48}$ 6. $\frac{5}{18} + \frac{4}{27} = \frac{5 \times 3 + 4 \times 2}{54} = \frac{15 + 8}{54} = \frac{23}{54}$ 7. $\frac{19}{42} - \frac{3}{28} = \frac{19 \times 2 - 3 \times 3}{84} = \frac{38 - 9}{84} = \frac{29}{84}$ 8. $\frac{8}{9} - \frac{5}{6} + \frac{1}{3} = \frac{8 \times 2 - 5 \times 3 + 1 \times 6}{18} = \frac{16 - 15 + 6}{18} = \frac{7}{18}$ 9. $\frac{9}{16} + \frac{5}{6} - \frac{7}{24} = \frac{9 \times 3 + 5 \times 8 - 7 \times 2}{48} = \frac{27 + 40 - 14}{48} = \frac{53}{48} = 1\frac{5}{48}$ 11. 1) $\frac{17}{48} + \frac{5}{32} = \frac{17 \times 2 + 5 \times 3}{96} = \frac{34 + 15}{96} = \frac{49}{96}$ (часть) — прошли во второй день. 2) $\frac{17}{48} + \frac{49}{96} = \frac{34 + 49}{96} = \frac{83}{96}$ (часть) — за два дня. **Ответ: $\frac{83}{96}$** 12. 1) $3\frac{1}{6} - 1\frac{1}{4} = 3\frac{2}{12} - 1\frac{3}{12} = 2\frac{14}{12} - 1\frac{3}{12} = 1\frac{11}{12}$ (ч) — из B в C. 2) $3\frac{1}{6} + 1\frac{11}{12} = 3\frac{2}{12} + 1\frac{11}{12} = 4\frac{13}{12} = 5\frac{1}{12}$ (ч) — весь путь. **Ответ: $5\frac{1}{12}$ ч** 13. $(x + \frac{5}{12}) - \frac{9}{20} = \frac{11}{15}$ $x + \frac{5}{12} = \frac{11}{15} + \frac{9}{20} = \frac{44 + 27}{60} = \frac{71}{60}$ $x = \frac{71}{60} - \frac{5}{12} = \frac{71 - 25}{60} = \frac{46}{60} = \frac{23}{30}$ **Ответ: $\frac{23}{30}$** 14. $\frac{4}{5} - (x + \frac{1}{60}) = \frac{2}{3}$ $x + \frac{1}{60} = \frac{4}{5} - \frac{2}{3} = \frac{12 - 10}{15} = \frac{2}{15}$ $x = \frac{2}{15} - \frac{1}{60} = \frac{8 - 1}{60} = \frac{7}{60}$ **Ответ: $\frac{7}{60}$**