1) 5х-4+2х=7(х-3)

     5х-4+2х=7х-3

      5х+2х-7х=-3+4

      х=1

2) 7-0.2x-(21.28-1.6)=0

     7-0.2x-21.28+1.6=0

      -0.2х=-1.6+21.28-7

       -0.2х = 12.68

        х= 12.68 : (- 0.2)

        х=-63.4

3)1/2x-3-(2-1/3x)=0

     1/2х-3-2+1/3х=0

     1/2х+1/3=3+2

      5/6х=5

       х=5: 5/6

        х=6

4)6/5-0.5x-0.4+2/5x=0

     -0.5х+2.5х=-6/5+0.4

        2х=-0.8

      х=-0.8 : 2

х= -0.4