If White has a queen, knight, and king and Black has only his king, then White wins with the same setup described in "Two Queens and King vs. King." (Of course, if kings are not connected, then the win is trivial as in "Queen and King vs. King".) For example, consider:
8/8/8/8/8/3Q4/8/KkN5 w
White to Move and Win
1. Na2 Kb2 2. Qb1 Ka3 3. Qb2+ Ka4 4. Qb4#
In this last example, White achieved the desired set-up with Black to move. If White must move, then he can triangulate his queen (take three moves with his queen to get back to the setup but with Black to move). For example, consider:
8/8/8/8/1N6/k7/8/KQ6 w
White to Move and Win
1. Na2 Kb2 2. Qc2 Kb1 (2. ... Ka3 3. Qb2+ Ka4 4. Qb4#) 3. Qc1 (not 3. Qb2?? stalemate) Kb2 4. Qb1 (triangulation complete) Ka3 5. Qb2+ Ka4 6. Qb4#