6х + 7 = 3 + 2х
6х - 2х = 3 - 7
4х = - 4
х = - 1
--------------------------------
5х - 12 = 8х - 3
5х - 8х = 12 - 3
- 3 х = 9
х= - 3
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х - 4 = 8 - х
х + х = 8 + 4
2х = 12
х = 6
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х - 10 = -13 -2х
х + 2х = 10 - 13
3х = - 3
х = - 1
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