1. x+(x+1)+(x+2)=9
x+x+1+x+2=9
3x+3=9
3x=9-3
3x=6
x=6:3
x=2
2. (z-2)+(z-1)+z=-3
z-2+z-1+z=-3
3z-3=-3
3z=-3+3
3z=0
z=0
3. 21+(20-4x)-(11-2x)=0
21+20-4x-11+2x=0
-2x+30=0
-2x=-30
x=-30:(-2)
x=15
4. 2u-3(7-2u)=3
2u-21+6u=3
8u=3+21
8u=24
u=24:8
u=3
5.12-y=5(4-2y)+10
12-y=20-10y+10
-y+10y=30-12
9y=18
y=18:9
y=2
6. 2-2(x-8)=4x-4
2-2x+16=4x-4
-2x-4x=-4-16-2
-6x=-22
x=-22:(-6)
x=11/3