By solving it graphically, I presume the question means draw the graph, and read off the answer from the point where the lines cross.
To do that, you need to draw each of the two lines.
Start with the first one: y-x+4=0. You need to find two points on that line, then use your ruler to draw the straight line that joins them. Any ttwo points will do, but the intercepts, where x=0 and where y=0 are usually good.
So, when x=0, we have y-0+4=0, or y=-4, so one point is (0, -4)
When y=0, we have 0-x+4=0, or x=4, so the point (4,0) is on this line.
Draw the line passing through (0,-4) and (4,0).
Now do the same for the other line.
The two lines cross at your answer, and you can read off both x and y. (Check: You should see that x=6 at your answer)