2x+y=6.
x-2y= -2

4x+y= -7.
x+4y=2

2x-5y= -7.
5x-y=9

3x-y=7.
2x-3y=1

1)
y=6-2x
x-2y=-2

x-2(6-2x)=-2
x-12+4x=-2
5x-12=-2
5x=-2+12
5x=10
x=2
y=6-2*2
y=6-4
y=2

2)
y=-7-4x
x+4y=2

x+4(-7-4x)=2
x-28-16x=2
-15x-28=2
-15x=2+28
-15x=30
x=-2
y=-7-4*(-2)
y=-7+8
y=1

3.
2x-5y=-7
y=-9+5x

2x-5*(-9+5x)=-7
2x+45-25x=-7
-23x*45=-7
-23x=-7-45
-23x=-52
x=52/23
y=-9+5*52/23
y=-9+260/23
y=53/23

4.
y=-7+3x
2x-3y=1

2x-3(-7+3x)=1
2x+21-9x=1
-7x+21=1
-7x=1-21
-7x=-20
x=20/7
y=-7+3*20/7
y=-7+60/7
y=11/7