So here is the weird story...
I was solving questions from a chapter of a book that was about equation solving and system of equations and the book subjects are precalculus algebra.and there was question there which I was not able to solve it.So I asked it on link and I tagged question with with systems-of-equations , algebra-precalculus and polynomials. After the time passed and comments and answers started to showing up, it became obvious that the question is related to algebraic-geometry and calculus which I don't know about this topics and my knowledge is very minimum there.
So my questions and problems are
1- As the two answers on my question are not related to the tags subjects that I have chosen for my question, why those answers are posted when they won't have a benefit for OP. Albeit thanks to people who put time and effort to answer my questions, but isn't tags are a sign of which topics OP is familiar with them? They could have asked me in comments about that I'm familiar with those topics or not, So then posting their answers.
2-As it turned out that the question is not solvable with precalculus techniques,and there solutions that are related to other topics like calculus, should I change the tags of my questions? As I think people who are familiar with those topics could benefit from this question and its answers.
3-As it is my fault that asking this question which is not in the topics that I familiar with them and there are two answer that seems to be right and useful, what should I do about accepting answer?