6х + 4 = 2х + 12
6х - 2х = 12 - 4
4х = 8
х = 2
-----------------------------------
8х + 4 + х = 2х + 25
9х - 2х = 25 - 4
7х = 21
х = 3
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5/18 * 54/100 - 5/18* 72у/10 - 4/19*76/100 + 4/19*38у/10 = 0,002
3/20 - 2у - 4/25 + 4у/5 = 0,002 общ.знамен.= 100
15 - 200у - 16 + 80у = 0,2
- 120у = -15 + 16 + 0,2
- 120у = 1,02
у = - 0, 0085