Help me find a challenge/math sub!

I’m looking for a sub that can help me with a challenge, a local gallery made a Christmas tree made of books and who guesses the number of books that the tree has wins a prize, I’m looking for a sub that I can post the pic of the tree and they can help me calculate, I know Math can’t help with this, and the other ones are about homework’s, there is a sub that can help me with this challenge?