3) 11/16 - 5/8 6) 4/15 + 7/12

Решение:

1. 3)
   \[ \frac{11}{16} - \frac{5}{8} = \frac{11-10}{16} = \frac{1}{16} \]
2. 6)
   \[ \frac{4}{15} + \frac{7}{12} = \frac{16+35}{60} = \frac{51}{60} = \frac{17}{20} \]

Ответ: 3) 1/16; 6) 17/20