I'm interested in the following question: https://math.stackexchange.com/q/1851713/84976 and I'd like to provide an answer. The problem is that the question has been closed (maybe before the last edit it wasn't clear). What can I do? Should do I ask the question newly by myself?
First: The question was closed for lack of context and I completely agree with this closure. Part of the purpose of closing questions is to prevent more answers to be added.
That said, I agree with the comment by Martin Sleziak above. I would say to leave it as is for some time. Give the OP an opportunity to add context to the question. If this doesn't happen within a day or two, I would find it completely fine to repost the question with context. I suggest adding a link to the closed question and explain your reasoning for your interest in the question. While many of us don't like questions without context, there is still some discussion on what exactly constitutes context. IMO you can in this specific case provide context by simply explaining where the question comes from and why you find the question interesting. Please also say in the question that you plan to answer the question yourself. (You can post the answer at the same time you post the question.) That way people will know that you aren't just trying to get someone to do your homework.