Okay,
The easiest way to do this would be to turn them both into Slope-Intercept form which is Y=mx+b
So, 6x+3y=9
Move 6x to the other side by subtracting it from both sides
3y= -6x+9
To graph that you would put a point on Positive 9 on the Y axis (the vertical one) and then go up 6 and left 1.
For Y=-2x+3
Put a point on 3 on the Yaxis and go up 2, left one