You can plot lines by extrapolating two points and connecting them. To extrapolate points on the graph, choose whatever value for x you like, and calculate the correspondent y value.
Line y = x+4:


Line y = -x-6:


Now draw the first two points (0,4) and (1,5) and connect them. You have the first line. Draw the last two points (-3,-3) and (-6,0) and connect them. You have the second line.
You should find out that the two lines cross at (-5,-1)