In the future please post your code usind <> on the toolbar so we can copy it. It's a little more tricky:
s = NDSolve[{D[u[x, y], x, x] + D[u[x, y], y, y] - 3 u[x, y] == x y,
u[0, y] == 0, (D[u[x, y], x] /. x -> 2) == 0, u[x, 0] == 0,
u[x, 1] == 0}, u, {x, 0, 2}, {y, 0, 1}]
Plot3D[u[x, y] /. s[[1]], {x, 0, 2}, {y, 0, 1}]