Ответ:

Пошаговое объяснение:

у - 5/7у = 2/9

7/7у - 5/7у = 2/9

2/7у = 2/9

у = 2/9 : 2/7

у = 2/9 * 7/2

у = 7/9

2 1/14 - 1 2/3х = 1 5/21

1 2/3х = 2 1/14 - 1 5/21

1 2/3х = 2 3/42 - 1 10/42

1 2/3х = 87/42 - 52/42

5/3х = 35/42

5/3х = 5/6

х = 5/6 : 5/3

х = 5/6 * 3/5

х = 3/6

х = 1/2

8/15 + 2/9у = 2 * 3/5

8/15 + 2/9у = 6/5

2/9у = 6/5 - 8/15

2/9у = 18/15 - 8/15

2/9у = 10/15

2/9у = 2/3

у = 2/3 : 2/9

у = 2/3 * 9/2

у = 9/3

у = 3