5х/12 - 4х/15 = х/20 + 1
25х/60 - 16х/60 = х/20 + 1
9х/60 - х/20 = 1
9х/60 - 3х/60 = 1
6х/60 = 1
6х = 1 * 60
6х = 60
х = 60 : 6
х = 10
х/3 - 2х/9 = х/6 + 1/2
3х/9 - 2х/9 = х/6 + 1/2
х/9 - х/6 = 1/2
2х/18 - 3х/18 = 1/2
- х/18 = 1/2
- х = 1/2 * 18
- х = 9
х = - 9