Thanks, Eirc.
Can I use {} instead of &&, such as "RegionPlot [{x<1/3,y<=1+x/2},{x,0.5},{y,o,1.5}]" But, I have a slightly different graph?
Also, let's say if there are five inequality functions, then, can I still use the same command: RegionPlot, and fill the space within all the functions?
Thanks!