Вычислите: 2) $$8\frac{5}{12} - 6\frac{7}{20} =$$ 3) $$9\frac{8}{21} + 4\frac{11}{14} =$$ 4) $$8\frac{5}{9} + 7\frac{3}{4} + 12\frac{7}{12} =$$

Решение:

2) $$8\frac{5}{12} - 6\frac{7}{20} = 8\frac{25}{60} - 6\frac{21}{60} = (8-6) + \frac{25-21}{60} = 2 + \frac{4}{60} = 2 + \frac{1}{15} = 2\frac{1}{15}$$

3) $$9\frac{8}{21} + 4\frac{11}{14} = 9\frac{16}{42} + 4\frac{33}{42} = (9+4) + \frac{16+33}{42} = 13 + \frac{49}{42} = 13 + 1\frac{7}{42} = 14\frac{7}{42} = 14\frac{1}{6}$$

4) $$8\frac{5}{9} + 7\frac{3}{4} + 12\frac{7}{12} = 8\frac{20}{36} + 7\frac{27}{36} + 12\frac{21}{36} = (8+7+12) + \frac{20+27+21}{36} = 27 + \frac{68}{36} = 27 + 1\frac{32}{36} = 28\frac{32}{36} = 28\frac{8}{9}$$

Ответ:

2) $$2\frac{1}{15}$$

3) $$14\frac{1}{6}$$

4) $$28\frac{8}{9}$$