Answer:
1. 7x-y=-3
y=mx+b
y=7x+3
7x-y=-3
2. 3x+y=-4
y=-3x-4
3x+y=-4
3. x-2y=-4
y=1/2x+2
1/2x-y=-2
(2)(1/2x-y)=-2(2)
x-2y=-4
4. 2x+3y=6
y=-2/3x+2
2/3x+y=2
(3)(2/3x+y)=2(3)
2x+3y=6
5.5x-y=5
y=5x-5
5x-y=5
6. 2x+y=5
y=-2x+5
2x+y=5
7. 3x-y=0
y=3x+0
3x-y=0