See the linked question on Math SE:
The OP and others were confused about whether "the number of people who do not know an odd number of people" refers to
People who know an even number of people, or
People for whom the number of people they do not know is odd.
I'm aware that option 1 is the correct choice, and I answered the question without thinking twice. But someone whose first language wasn't English had no idea how to interpret it, and I attempted to explain why option 1 was correct. My attempt was poor. Can anyone here do better?