I agree with AdamLein, but to play along with the brainteaser:
The sailboat on the port tack
1) is give-way to the sailboat on the starboard tack
2) is stand-on to the power boat
The sailboat on the starboard tack
1) is give-way to the power boat (he's overtaking the powerboat)
2) is stand-on to the sailboat on a port tack
The power boat
1) is give-way to the sailboat on the port tack
2) is stand-on to the overtaking sailboat on the starboard tack
Like AdamLein said the rules are for each boat relative to one another and the problem comes in because the rules stated above
don't specifically account for the scenario above. However, there are rules that do account for the "failure" of the specific rules, like:
RULE 17 - STAND-ON VESSEL
b) When, from any cause, the vessel required to keep her course and speed finds herself so close that collision cannot be avoided by the action of the give-way vessel alone, she shall take such action as will best aid to avoid collision.
Basically everyone has the ultimate responsibilty to avoid collision regardless of the rules and whether the vessel is a stand-on, give-way or even both.