1)6x-2(x-2)=12-4x
6x-2x+4=12-4x
4x+4=12-4x
4x+4x=12-4
8x=8
X=8/8
X=1
2)x+y=6
x-y=4
x+y=6
x=4+y
4+2y=6
2y=6-4
2y=2
y=2/2
y=1
x=4+1
3)2x+3y=0
x-y=5
2x+3y=5
x=5+y
2(5+y)+3y=0
10+2y+3y=0
10+5y=0
5y=0-10
5y=-10
y=-10/5
y=-2
X=5-2
X=3
