2/3
-------------- + 1/3 = 7/9
5/6х - 1/6
2/3
--------------- = 7/9 - 1/3
5/6х - 1/6
2/3
--------------- = 7/9 - 3/9
5/6х - 1/6
2/3
-------------- = 4/9
5/6х - 1/6
5/6х - 1/6 = 2/3 : 4/9
5/6х - 1/6 = 2/3 * 9/4
5/6х - 1/6 = 1/1 * 3/2
5/6х - 1/6 = 3/2
5/6х = 3/2 + 1/6
5/6х = 9/6 + 1/6
5/6х = 10/6
х = 10/6 : 5/6
х = 10/6 * 6/5
х = 10/5
х = 2