Order questions depending on answer votes
Something like:

SELECT q.*, SUM(a.votes_up) - SUM(a.votes_down) AS TotalVotes
FROM Questions AS q
JOIN Answers AS a ON a.QuestionID = q.QuestionID
GROUP BY q.QuestionID, q.Question, q.AnyOtherFieldFromThatTable
ORDER BY TotalVotes DESC;


I would encourage you to include q.QuestionID (or whatever you call that field) in your GROUP BY clause, for performance reasons.