problem solving vs mentation

problem solving and mentation both are nouns.

Word	Noun	Adjective	Verb	Adverb
problem solving	Yes	No	No	No
mentation	Yes	No	No	No

As nouns, mentation is a hypernym of problem solving; that is, mentation is a word with a broader meaning than problem solving:

Other hypernyms of problem solving include cerebration, intellection, thinking, thought, thought process.

problem solving (noun)	mentation (noun)
the thought processes involved in solving a problem	the process of using your mind to consider something carefully
the area of cognitive psychology that studies the processes involved in solving problems