Help us caption and translate this video on Amara.org: http://www.amara.org/en/v/B2wY/ Traduzione In Italiano del Video Passing Trains http://www.youtube.com/watch?v=qLLjD-g_9ms http://www.khanacademy.org/video/passing-trains?playlist=Algebra Help us caption & translate this video! http://amara.org/v/B2wY/