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

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

Ответ: 1) \(20\frac{13}{24}\); 3) \(14\frac{1}{6}\).