Assuming that the horizontal axis is for a and the vertical axis is for b,
- Cover up 2a so you get the equation 3b = 6 which gives b = 2.
- Mark the point (0, 2) on the coordinate plane.
- Cover up 3b so you get the equation 2a = 6 which gives a = 3.
- Mark the point (3, 0) on the coordinate plane.
- Join the two points and extend the line in both directions.
Done!
