Ответ:

1/2

Пошаговое объяснение:

2 - 1 8/21х = 13/14 + 8/21

2 - 1 8/21х = 39/42 + 16/42

2 - 1 8/21х = 55/42

2 - 1 8/21х = 1 13/42

1 8/21х = 2 - 1 13/42

1 8/21х = 1 42/42 - 1 13/42

29/21х = 29/42

х = 29/42 : 29/21

х = 29/42 * 21/29

х = 1/2 * 1/1

х = 1/2