Ответ:

- 23/42

Пошаговое объяснение:

1 13/14 - (6 - 5 11/35) : 9/25 + 4/21

1 13/14 - (1 - 11/35) : 9/25 + 4/21

1 13/14 - (35/35 - 11/35) : 9/25 + 4/21

1 13/14 - 24/35 : 9/25 + 4/21

1 13/14 - 24/35 * 25/9 + 4/21

1 13/14 - 8/7 * 5/3 + 4/21

1 13/14 - 40/21 + 4/21

1 13/14 - 1 19/21 + 4/21

13/14 - 19/21 + 4/21

26/42 - 57/42 + 4/21

-31/42 + 4/21

4/21 - 31/42

8/42 - 31/42 = -23/42