[Заголовок обрезан] 2) 12 3/8 + 8 1/6; 3) 9 8/21 + 4 11/14; 4) 8 5/9 + 7 3/4 + 12 7/12.

1. \(12\frac{3}{8}+8\frac{1}{6}=20+\frac{9}{24}+\frac{4}{24}=20\frac{13}{24}\).
2. \(9\frac{8}{21}+4\frac{11}{14}=13+\frac{16}{42}+\frac{33}{42}=14\frac{1}{6}\).
3. \(8\frac{5}{9}+7\frac{3}{4}+12\frac{7}{12}=27+\frac{20+27+21}{36}=28\frac{8}{9}\).

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