Sketch the region bounded by the graphs of the equations?

You have to sketch this? It's three dimensional! The first equation is that of a sphere centered a the origin, of radius 2. The last equation represents the xy plane, so the first and third equations together represent the top half of a sphere. The second equation is that of a plane intersecting the zy plane in the line z = .5y, thus slicing part of the top half of the sphere. Good luck with the drawing though. There are several freeware graphing utilities that can do this for you. Search freeware graphers, or, if you have a mac, just use the grapher that comes with it.