Given
3x-6y=-12
x-2y=8
You're going to try to cancel each variable by multiplying the opposite number only for one equation
-3(x-2y=8)
Your new equations will look like this:
3x-6y=-12
-3x+6y=4
The first equation is still the same, now cancel out
-12
4
Answer: no solution
I hope this helped! :-)