8 9/26 - z = 5 7/39
-z = 5 7/39 - 8 9/26
z= 8 9/26 - 5 7/39
z = 217/26 - 202/39
z = ( 651 - 404)/78
z = 247/78 (сократим дробь на 13)
z = 19/6
z= 3 1/6
(5/6 +x ) - 2/3 = 13/18
5/6 +x = 13/18 + 2/3
5/6 +x = 13/18 +12/18
5/6 +x = 25/18
x= 25/18 - 5/6
x= 25/18 - 15/18
x= 10/18 (сократим дробь на 2)
x=5/9