Well the first equation is in General form Ax + By = c. So you have to rearrange it into slope intercept form y = mx + c. So the equation -2y + x = -8 can be rearranged to become y = -0.5x + 4. That's the first equation. m = -0.5 or -1/2 and c = 4. Therefore using rise over run from 4 you can easily graph it.
The second equation also needs to be rearranged into slope intercept form y = mx + c. The equation 0 = -x + 4 - 2y can be rearranged to 2y = -x + 4 then to y = -0.5x + 2. Hence m = -0.5 or -1/2 and c = 2. Therefore you now have all the information plot the two equations. If you need any clarification or questions feel free to ask me.