Question
Three boats, A, X and B, are reaching on proper courses. B is approximately two lengths line astern of A, and X is overlapped to windward of B. A slows, intending to luff X. X hails for room to pass to leeward of A and bears away. B protests. What should the call be?

Answer
A is a right-of-way boat and is therefore an obstruction to X and B. However at position 1 X is about to pass it to windward and B is about to pass it to leeward, so rule 18 does not apply between them at this time.
Because A is an opponent who can be expected to luff X if X attempts to pass to windward, passing A to leeward is a proper course for X. Therefore X does not break rule 17.2 by bearing away to pass A to leeward.
Once X has borne away, X and B are about to pass A on the same side. Rule 18.2(a) applies and X is entitled to room. No penalty.
However, if B chooses to pass A to windward, then this too is a proper course, and X must keep clear.