Question 23200
Graph the line y= (12-3x)/4 = (-3/4)x+4 as a dashed line.
Shade the area below it.
Graph the line y=(6-x)/3= (-1/3)x+2 as a dashed line.
Shade the area below it.
Graph the ray x=0 (shade area to the right)
Graph the y=0 (shade area above)
Determine where y = (-3/4)x+4 and y= (-1/3)x+2 intersect 
the x axis. 
Determine the area in the 1st quadrant that is the intersection
of all the shaded areas.
That is the solution space for your system of inequalities.

Cheers,
Stan H.