I learned the question above in college as "Lincoln's riddle"* and it comes to mind every time Rachel does a segment about how these "budget bills" aren't really about budgets. The answer to the riddle is four, because simply calling a tail a leg doesn't make it one. Similarly, calling an anti-union bill padded with culture war measures a "budget repair bill" doesn't make it one.
*For a really outstanding exploration of the origin of the riddle, this Snopes thread is fascinating. (Short version: Apparently 19th century, but definitely pre-dating Lincoln.)