In the first sentence, it seems to me that to know expresses that the speaker experienced the problem/difficulty. You would use the present perfect to express something that happened previously, without specifying the time. Please let me know as soon as you figure it out.
'know of' is used when you have personal. I know how to drive a car. I know (about) this difficulty/problem.
Recently one of my friends told me that there is distinct difference between 'know of something' and 'know about something' expressions. It's not just you that don't know. I saw this sentence in the book 1q84: In (2), however, the object of.
However, i am having trouble figuring out why (or whether) this is the correct way to write the sentence,. What is the correct usage of phrase you don't know what you don't know? Also explain the difference between the two, thanks. Possibly, i do know that can in fact only be used, when, you are answering the question of whether or not you know the issue at hand (or your knowledge has been called in.
Alright, well, for example, like on saturdays, y’know, what i liked to do. Why would you have a problem with this?