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) \(8\frac{5}{9} + 7\frac{3}{4} + 12\frac{7}{12}\)

Решение:

1. \( 12\frac{3}{8} + 8\frac{1}{6} = (12 + 8) + (\frac{3}{8} + \frac{1}{6}) = 20 + \frac{3 \times 3 + 1 \times 4}{24} = 20 + \frac{9+4}{24} = 20 + \frac{13}{24} = 20\frac{13}{24} \)


2. \( 3\frac{13}{15} + 6\frac{7}{10} = (3 + 6) + (\frac{13}{15} + \frac{7}{10}) = 9 + \frac{13 \times 2 + 7 \times 3}{30} = 9 + \frac{26+21}{30} = 9 + \frac{47}{30} = 9 + 1\frac{17}{30} = 10\frac{17}{30} \)


3. \( 9\frac{8}{21} + 4\frac{11}{14} = (9 + 4) + (\frac{8}{21} + \frac{11}{14}) = 13 + \frac{8 \times 2 + 11 \times 3}{42} = 13 + \frac{16+33}{42} = 13 + \frac{49}{42} = 13 + 1\frac{7}{42} = 13 + 1\frac{1}{6} = 14\frac{1}{6} \)


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