Just by moving one match you can turn the math problem into a correct answer. Definitely use this to get some free drinks. And you already know the answer, so it won't be hard. If you want to try and figure this one out for yourself, pause the video before the reveal.
Fun Party Tricks provides tons of great howto videos for cool party tricks. These videos are free and easy magic tricks that allow you to show off your skills at a party or bar.