50. Найдите сумму: 1) \(12\frac{3}{8} + 8\frac{1}{6};\) 2) \(3\frac{13}{15} + 6\frac{7}{10};\) 3) \(9\frac{8}{21} + 4\frac{11}{14};\) 4) \(8\frac{5}{9} + 7\frac{3}{4} + 12\frac{7}{12}.\)

Выполним вычисления:

1. \(12\frac{3}{8} + 8\frac{1}{6} = 12 + 8 + \frac{3}{8} + \frac{1}{6} = 20 + \frac{3 \cdot 3}{8 \cdot 3} + \frac{1 \cdot 4}{6 \cdot 4} = 20 + \frac{9}{24} + \frac{4}{24} = 20 + \frac{9 + 4}{24} = 20 + \frac{13}{24} = 20\frac{13}{24}\)
2. \(3\frac{13}{15} + 6\frac{7}{10} = 3 + 6 + \frac{13}{15} + \frac{7}{10} = 9 + \frac{13 \cdot 2}{15 \cdot 2} + \frac{7 \cdot 3}{10 \cdot 3} = 9 + \frac{26}{30} + \frac{21}{30} = 9 + \frac{26 + 21}{30} = 9 + \frac{47}{30} = 9 + 1\frac{17}{30} = 10\frac{17}{30}\)
3. \(9\frac{8}{21} + 4\frac{11}{14} = 9 + 4 + \frac{8}{21} + \frac{11}{14} = 13 + \frac{8 \cdot 2}{21 \cdot 2} + \frac{11 \cdot 3}{14 \cdot 3} = 13 + \frac{16}{42} + \frac{33}{42} = 13 + \frac{16 + 33}{42} = 13 + \frac{49}{42} = 13 + 1\frac{7}{42} = 14\frac{7}{42} = 14\frac{1}{6}\)
4. \(8\frac{5}{9} + 7\frac{3}{4} + 12\frac{7}{12} = 8 + 7 + 12 + \frac{5}{9} + \frac{3}{4} + \frac{7}{12} = 27 + \frac{5 \cdot 4}{9 \cdot 4} + \frac{3 \cdot 9}{4 \cdot 9} + \frac{7 \cdot 3}{12 \cdot 3} = 27 + \frac{20}{36} + \frac{27}{36} + \frac{21}{36} = 27 + \frac{20 + 27 + 21}{36} = 27 + \frac{68}{36} = 27 + 1\frac{32}{36} = 28\frac{32}{36} = 28\frac{8}{9}\)

Ответ: 1) \(20\frac{13}{24}\); 2) \(10\frac{17}{30}\); 3) \(14\frac{1}{6}\); 4) \(28\frac{8}{9}\)