25 - 7 + 2х = 5х
2х - 5х = - 25 + 7
- 3х = - 18
х = 6
-----------------------------------
6х - 27 = 5х - 20
6х - 5х = 27 - 20
х = 7
-------------------------------------
5 -3х = 2х - 8
-3х - 2х = - 8 -5
- 5х = - 13
х = 2,6
-----------------------------
21 - 14х = 15 - 15х
-14х + 15х = - 21 + 15
х = - 6
-----------------------------
2х + 40 = х + 14
2х - х = - 40 + 14
х = - 26
-----------------------------------
7х - 3 - 2х = х + 9
7х - 2х - х = 9 + 3
4х = 12
х = 3