Puzzle 065 in Professor Layton and the Diabolical Box (US) / Pandora's Box (EU) is located in Chapter 5 or 6, typically within the Folsense area. Exact NPC and screen vary slightly by region (US vs EU numbering differs by ~1-2 puzzles).
It's a logic/math puzzle typical of the mid-game difficulty spike. Often involves:
Tip: If stuck, use Hint Coins (3 per puzzle). The Super Hint (2 coins) practically gives the answer. Coins are plentiful—tap every background object in every scene.
Note: Verify your region (US/EU) before following a guide. Puzzle numbers shift slightly.