Here it is. The verification involves doing it the long way too, which takes 6 surface integrals. Fortunately each component of the function F is 0 when that variable is 0 so the faces of the cube have no flux at the faces of the cube lying in any coordinate plane. Let me know if you have questions.
Verify that the Divergence Theorem is true for the vector field F on the region e. Give the flux. F(x, y, z) = 2xi + xyj + 3xzk, E is the cube bounded by the planes x = 0, x = 3, y = 0, y = 3, z = 0, and z = 3.