3) (5 6/7+3 5/21)×2 1/10
4) (7 5/12-3 1/6)×2 2/17

Пошаговое объяснение:

3.

1) 5. 6/7 + 3. 5/21 = 5. 18/21 + 3. 5/21 = 8. 23/21 = 9. 2/21

2) 9. 2/21 * 2. 1/10 = 191/21 * 21/10 = 191/10 = 19. 1/10

4.

1) 7. 5/12 - 3. 1/6 = 7. 5/12 - 3. 2/12 = 4. 3/12 = 4. 1/4

2) 4. 1/4 * 2. 2/17 = 17/4 * 36/17 = 36/4 = 9