7.
9.
11.
13. Use the symmetry and homogeneity of the region to look only at the front left half (viewed from the usual perspective) and double that, producing .
15. It's an ugly problem, but if forced to do it here's what I'd do: First pull a trick, and interchange the x and z axes, so we're finding the integral of the function z for the region E bounded by z = 4x2 + 4y2 and the plane z = 4. Yes, you can do that. Then the integral sets up most easily in polar (or cylindrical, to be proper) coordinates as .
17. It's a tetrahedron with intercepts (6,0,0), (0,4,0), and (0,0,2). The most natural integral is .
19. .