Помогите решить:

1) x - (50-x) = 12

2) (18-3x) - (4+2x) = - 6

3) (z-2) + (z-1) + z=-3

4) 21 + (20-4x) - (11-2x) = 0

1) x - (50-x) = 12

х-50+х=12

2 х=50+12

2 х=62

х=62:2

х=31

2) (18-3x) - (4+2x) = - 6

18 - 3 х-4-2 х=-6

-3 х-2 х=-6-18+4

-5 х=-20

х = (-20) : (-5)

х=4

3) (z-2) + (z-1) + z=-3

z-2+z-1+z=-3

3z=-3+2+1

3z=0

z=0

4) 21 + (20-4x) - (11-2x) = 0

21+20-4x-11+2x=0

-4x+2x=11-21-20

-2x=-30

x = (-30) : (-2)

x=15