Puzzle 1:
Rack: 
Pool: 
TALL o6 (14) leaves GOY which plays at 12f or 10m while blocking your opponent’s out bingo SHARERS.
Puzzle 2:
Rack: 
QUEST l4 (30) keeps the L and U available to draw TRANQUIL on a future turn, scoring 60 points. In this case, the L and U are extremely valuable tiles.
Puzzle 3:
Rack: 
MODE 9h (26) allows you to keep proper board dynamics by playing in the middle of the board while keeping a good leave and giving yourself a MODE-L hook next turn if you happen to draw well.
Puzzle 4:
Rack: 
VAS f2 sets up an unblockable K-VAS hook, allowing you to play HOOK/KVAS (at a minimum) next turn for 40+ points.
Puzzle 5:
While it might be intuitive to play QUILT b6 and blocks the open U in the TW/TL alley, the best play is actually to use both of your Us and play UVULA j1 (24), creating a second lucrative lane for your U.