You do not need to find the intersection point. First you will need to find two two points on each line and then draw a line through these points. The lines will meet at the intersection points.
We will find two points on the graph.
==> let x= 1 ==> y = 2*1 = 2==> (1,2) is on the graph.
==> let y= 0 ==> y= 0 ==> The point (0,0) is on the graph too.
Now we will find the points on the graph and then connect between them with a line that we can extend far from the points.
The same for the line 3x-y = -2
==> let x= 1 ==> 3 -y= -2 ==> y= 5 ==> (1,5) on the graph.
==> x= 0 ==> y= 2 ==> (0,2) is on the graph.
Now we can draw a line between those points.