The phrase "a puzzle which" is correct and usable in written English.
It can be used when referring to a specific puzzle that is being described or explained.
Example: "I found a puzzle which challenges my problem-solving skills."
Alternatives: "a puzzle that" or "a puzzle where".
Gypsum soils are both a problem and a puzzle, which is precisely why they deserve attention.
"One of the options was to make a puzzle, which he presented today".
It is a puzzle which, as puzzles do, Dreams that there is no puzzle.
As an example, there was a puzzle which had images of a pen, some seashells, some butterflies and more.
Of course, Scott might reveal that Deckard is a special replicant with an extended lifespan: either way, Ford's presence would demand that a puzzle which has had film fans arguing for more than three decades finally be addressed.
Working out what the Cherry and Whites are going to do next is a puzzle which would strain the combined brains of Pythagoras, Einstein and Stephen Hawking, never mind poor David Humphreys.
Round 3 is a Prize Puzzle, which offers a prize (usually a trip) to the contestant who solves it.
It's always a pleasure to watch a keen mind absorbed in a difficult puzzle, which is how Dave Gurney distinguishes himself in John Verdon's tricky whodunits.
There he was in an old picture, she told the jurors, "doing a crossword puzzle, which was something Emile did quite a bit".
I also like the visual effect of a circular puzzle which, after cutting, ended up as a lacy snowflake inscribed with "[the] frolic architecture of [the] snow" from Emerson's poem The Snowstorm.
A final puzzle, which is making the predictions of sage pundits look a bit daft: this is proving to be a remarkably topsy-turvy series, yet the matches themselves have not been topsy-turvy at all.
