What a neat mathematical problem is worth? (4,3)
I believe the answer is:
'worth?' is the definition.
The answer and definition can be both quantities as well as being singular nouns.
Maybe there's an association between them I don't understand?
'what a neat mathematical problem' is the wordplay.
'what a neat' becomes 'tidy' (synonyms).
'mathematical problem' becomes 'sum' (I've seen this before).
'is' is the link.
Can you help me to learn more?
(Other definitions for tidy sum that I've seen before include "A lot of money" , "Considerable amount" .)