Originally Posted by
sperk Как "не могу знать" отличается от "не знаю"?
Спасибо
That is an outdated variant usually used by a subordinate addressing a superior and it means something like "I am sorry, but I don't know, I can't know that, I am only a cog, an underling, so don't ask me and please don't make me responsible".
Briefly, "I don't know, and knowing that is not my duty". The phrase, anyway, means sycophancy.
P.S. Your question sounds okay, but "
чем отличается..." would make your sentence perfect.