by timmydoeslsat Wed May 30, 2012 5:55 pm
You are missing the N variable!
You can start this diagram from this:
_ _ _ ...N
R P X ...this is reversible with P always in the middle of those two.
_ _ _ ...O
We also know that S and U cannot be beside N, this means that at least one of S/U must be in that third row. What I would concentrate on now is that we have the other of U/S, T, and an X left to place.
In regards to #3, if S and U are in the same row, we know that this will be the third row with O, and we have no order of these three as no rules govern that. We now know that the X and T will join N. Again, no rules governing that arrangment either. So T and N can sit beside the X. The testwriters choose for T to be the answer choice.