(2 7/9 z+3 1/3)*3/5 равно 1/6 z+6 1/2
2 7/9z + 3 1/3 = (1/6 + 6 1/2) х 5/3
25/9z + 10/3 = 5/18z + 65/6
25/9z - 5/18z = 65/6 - 10/3
15/18z = 45/6
z = 6