Of course, but dont you also need 3X the shaders for 3x the pixels, etc? I'm not that technically smart but I think we can make very rough estimations.
Of course as well, but again for fun you can do it very roughly, knowing it is not accurate though.
For Xbox, figure it's a 4 pipe GPU at 233. Figure Xenos is 48 ALU.8 for vertexs, break it down like a "traditional card", figure it being like a 20 pipe card. 20 to 5. So you're at 5X. But then we have to double the clockspeed roughly. So you're at 10X. This does not account for differences in the pipes (xenos pipes might be better, being more modern, then again a pipe is a pipe they haven't changed much), other architecture differences (should be mostly improvements by Xenos), Memory speeds (have not scaled as well as pipes so may be a negative) etc. But roughly 10X might be a good try..
Of course there is a lot of approximations, but it's fun..