Substitute y=-x+6 x-2y=-6

x-4x+12=6

-3x+12=6

-3x+12-12=6-12

-3x=-6

-3x/-3=-6/-3

x=2

Plug (2) in for x in L2 and solve for y:

y=2 (2) - 6

y=4-6

y=-2

The solution (x, y) = (2,-2)

Check in both equations by substituting (x, y) = (2,-2) and see if it equals out:

L1) (2) - 2 (-2) = 6

2+4=6

6=6 L1 checks out.

L2) (-2) = 2 (2) - 6

-2=4-6

-2=-2 L2 checks out also, so we can say with confidence that the solution is right.