1) 4x -3(х-4)=5х-12

  4x -3x +12 = 5x - 12

  -4x= -24

  x = 6

2) 8х-7+3-21=х+10

  7x= 35

  x = 5

3) 2(х-8)=7(х-1)

  2x-16 = 7x - 7

  -5x = 9

  x = -9/5