P, Q, R, S, T, U, V and W are sitting around a circle facing the centre, with P second to the right of T, T the neighbour of R and V, and V the neighbour of U. Which two of the following are not neighbours?

R and V are not neighbours.

T's two neighbours are named as R and V, so they sit on opposite sides of T.

Being on opposite sides of T, R and V cannot be next to each other.

V also has U as its other neighbour, extending the chain R-T-V-U.

Thus R and V are separated by T and are not adjacent.

So the pair that are not neighbours is R and V.