2) 3 13/15 + 6 7/10 4) 8 5/9 + 7 3/4 + 12 7/12

Решение:

1. 2) 3 13/15 + 6 7/10
   \[ 3 \frac{13}{15} + 6 \frac{7}{10} = (3+6) + (\frac{13}{15} + \frac{7}{10}) = 9 + \frac{26+21}{30} = 9 + \frac{47}{30} = 9 + 1 \frac{17}{30} = 10 \frac{17}{30} \]
2. 4) 8 5/9 + 7 3/4 + 12 7/12
   \[ 8 \frac{5}{9} + 7 \frac{3}{4} + 12 \frac{7}{12} = (8+7+12) + (\frac{5}{9} + \frac{3}{4} + \frac{7}{12}) = 27 + \frac{20+27+21}{36} = 27 + \frac{68}{36} = 27 + 1 \frac{32}{36} = 28 \frac{8}{9} \]

Ответ: 2) 10 17/30; 4) 28 8/9