You have to put it into slope-intercept form.
4.5x-0.5y=3
1. Subtract 4.5x from both sides:
-0.5y=-4.5x+3
2. Divide both sides by -0.5 to leave the y variable on one side:
y=9x-6
3. Your linear equation is
y=9x-6
4. Graph (tell me if you need help on graphing!)