Найдите сумму: 1) 12 3/8 + 8 1/6 3) 9 8/21 + 4 11/14

Решение:

1. 1) 12 3/8 + 8 1/6
   \[ 12 \frac{3}{8} + 8 \frac{1}{6} = (12+8) + (\frac{3}{8} + \frac{1}{6}) = 20 + \frac{9+4}{24} = 20 + \frac{13}{24} = 20 \frac{13}{24} \]
2. 3) 9 8/21 + 4 11/14
   \[ 9 \frac{8}{21} + 4 \frac{11}{14} = (9+4) + (\frac{8}{21} + \frac{11}{14}) = 13 + \frac{16+33}{42} = 13 + \frac{49}{42} = 13 + 1 \frac{7}{42} = 14 \frac{1}{6} \]

Ответ: 1) 20 13/24; 3) 14 1/6