It's a linear function. We need only two points to the plotting of the graph.
[tex]3x+2y=12\qquad\text{subtract 3x from both sides}\\\\2y=-3x+12\qquad\text{divide both sides by 2}\\\\y=-\dfrac{3}{2}x+6\\\\for\ x=0\to y=-\dfrac{3}{2}(0)+6=0+6=6\to(0,\ 6)\\\\for\ x=4\to y=-\dfrac{3}{2}(4)+6=-6+6=0\to(4,\ 0)[/tex]