Questions & answers
Here are some places where questions can be asked about maths and hopefully answered.
“Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It’s 100% free, no registration required.”
mathoverflow.net is a place for professional mathematicians.
The longest running group that I am aware of is the usenet group sci.math. This can be accessed via Google Groups.
In years gone by I received helpful answers through this group, but like many unmoderated usenet groups this one has become over-run by nuisance posters.