As students are enrolling in pre-algebra and algebra in droves, I thought I would post this video, which is part 1 of a magic trick illustrating the mind-boggling power of algebra. It is very common to learn how to do algebra without learning why to do it. To me, this magic trick gives a sense of how useful and powerful the technique of algebra can be.
Part 1 ends with a mystery, including a $100 bounty for anyone who can find a counterexample to the trick. If you know a student (or are a student) who thinks you can find a way to break this trick, let me know if you do.