the your question does not meet our quality standards thing is really annoying...
I have wasted lots of time trying to figure out what this message means
It is an automatically generated message.
There is an algorithmic "quality filter" for questions. StackExchange has not published the formula, and there must be a lot of analysis of this on meta.stackoverflow, but it is safe to assume that the shorter the question the higher the chance of rejection. In your question, the math symbols are not in TeX and it is possible the filter has heuristics that correlate with that. Several alphabetic strings are not in the English dictionary and not written between dollar signs: b,lim,sqrt,x,x-.
As suggested in comment below the question, searches for (quality-filter) tag on meta.stackoverflow and meta.math.stackexchange.com might reveal more.
https://meta.stackoverflow.com/search?q=quality-filter $\hskip20pt$ 256 hits
http://meta.math.stackexchange.com/questions/tagged/quality-filter $\hskip20pt$ 9 hits
And for our friends the anonymous downvoters, here is a copy of the comment explaining why all this information is the only valid form of answer, until and unless the asker requests something different.
I interpret the question as "why did I get this message preventing me from posting (attached text)". To that, the only possible answer is some discussion of the quality filter. Answers that do not even mention the filter and give generalized advice assuming there was something "wrong" in the material stopped by the filter, are insulting when the OP did not request any such writing advice.