Here is the problem,

Show by direct computation that the centroid of the triangle with vertices (0,0), (r,0), and (0,h) is the point (r/3, h/3). Verify that this point lies on the line from the vertex (0,0) to the midpoint of the opposite side of the triangle and twothirds of the way from the vertex of the midpoint.

I really don't even know where to begin..