This is the 1124th most frequent Polish word.
problemu
"Problemu" means "of the problem" in English.
Here, 'problemu' is used in the genitive singular case, being the negative declension due to the context of 'nie ma.'
Nie ma żadnego problemu.
There is no problem.
In this sentence, 'problemu' is in the genitive singular case, because the phrase 'rozwiązanie tego' governs the genitive for 'problem.'
Znalazłem rozwiązanie tego problemu.
I found a solution to this problem.
Here, 'problemem' is in the instrumental singular case as it is used in conjunction with the preposition 'z' indicating manner or means.