Вычисли значения выражений с дробями в задании 269

Конечно, давай решим эти примеры вместе! 1) $\frac{3}{7} + \frac{4}{9} = \frac{27}{63} + \frac{28}{63} = \frac{55}{63}$ 2) $\frac{8}{9} - \frac{7}{8} = \frac{64}{72} - \frac{63}{72} = \frac{1}{72}$ 3) $\frac{13}{15} - \frac{2}{3} = \frac{13}{15} - \frac{10}{15} = \frac{3}{15} = \frac{1}{5}$ 4) $\frac{20}{21} + \frac{3}{7} = \frac{20}{21} + \frac{9}{21} = \frac{29}{21}$ 5) $\frac{17}{18} - \frac{11}{12} = \frac{34}{36} - \frac{33}{36} = \frac{1}{36}$ 6) $\frac{7}{16} + \frac{1}{6} = \frac{42}{96} + \frac{16}{96} = \frac{58}{96} = \frac{29}{48}$ 7) $\frac{2}{9} + \frac{5}{6} = \frac{4}{18} + \frac{15}{18} = \frac{19}{18}$ 8) $\frac{10}{21} + \frac{9}{14} = \frac{20}{42} + \frac{27}{42} = \frac{47}{42}$ 9) $\frac{7}{9} - \frac{4}{15} = \frac{35}{45} - \frac{12}{45} = \frac{23}{45}$ 10) $\frac{9}{14} - \frac{3}{7} + \frac{15}{28} = \frac{18}{28} - \frac{12}{28} + \frac{15}{28} = \frac{21}{28} = \frac{3}{4}$ 11) $\frac{1}{6} + \frac{1}{4} - \frac{1}{8} = \frac{4}{24} + \frac{6}{24} - \frac{3}{24} = \frac{7}{24}$ 12) $\frac{13}{18} - \frac{29}{45} + \frac{8}{15} = \frac{65}{90} - \frac{58}{90} + \frac{48}{90} = \frac{55}{90} = \frac{11}{18}$