In Puzzle 15, you should play BITE 10a, blocking the open QI 10a. BITE withholds the U and A for sUQ or QUA next turn while blocking your opponent’s primary Q spot. If you don’t draw the Q, you will be able to simply pass and stick your opponent with the Q on future turns. Your opponent is unlikely to block SUQ and QUA since any play that does so scores very poorly and requires using good tiles that your opponent often won’t have.