Решите примеры на сложение и вычитание дробей: 9/12 + 3/4, 8/9 + 1/3, 4/5 + 7/15, 2/21 + 5/14, 3/18 + 5/27, 3/15 + 7/20, 7/20 - 11/50, 17/33 - 5/22, 9/20 - 5/8, 4/7 - 13/28, 5/13 - 14/39.

5) **Ответ: 1.5** $\frac{9}{12} + \frac{3}{4} = \frac{3}{4} + \frac{3}{4} = \frac{6}{4} = 1.5$ 6) **Ответ: $1\frac{2}{9}$** $\frac{8}{9} + \frac{1}{3} = \frac{8}{9} + \frac{3}{9} = \frac{11}{9} = 1\frac{2}{9}$ 7) **Ответ: $1\frac{4}{15}$** $\frac{4}{5} + \frac{7}{15} = \frac{12}{15} + \frac{7}{15} = \frac{19}{15} = 1\frac{4}{15}$ 8) **Ответ: $\frac{19}{42}$** $\frac{2}{21} + \frac{5}{14} = \frac{4}{42} + \frac{15}{42} = \frac{19}{42}$ 9) **Ответ: $\frac{19}{54}$** $\frac{3}{18} + \frac{5}{27} = \frac{9}{54} + \frac{10}{54} = \frac{19}{54}$ 10) **Ответ: $\frac{11}{20}$** $\frac{3}{15} + \frac{7}{20} = \frac{1}{5} + \frac{7}{20} = \frac{4}{20} + \frac{7}{20} = \frac{11}{20}$ **Вариант 2 (Вычитание):** 1) **Ответ: $\frac{13}{100}$** $\frac{7}{20} - \frac{11}{50} = \frac{35}{100} - \frac{22}{100} = \frac{13}{100}$ 2) **Ответ: $\frac{19}{66}$** $\frac{17}{33} - \frac{5}{22} = \frac{34}{66} - \frac{15}{66} = \frac{19}{66}$ 3) **Ответ: $-\frac{7}{40}$** $\frac{9}{20} - \frac{5}{8} = \frac{18}{40} - \frac{25}{40} = -\frac{7}{40}$ 4) **Ответ: $\frac{3}{28}$** $\frac{4}{7} - \frac{13}{28} = \frac{16}{28} - \frac{13}{28} = \frac{3}{28}$ 5) **Ответ: $\frac{1}{39}$** $\frac{5}{13} - \frac{14}{39} = \frac{15}{39} - \frac{14}{39} = \frac{1}{39}$