posted by Shelby on .
Jon begins jogging at a steady 3m/sec down the middle of lane one of a public track. Laura starts even with him in the center of lane two but moves 4m/sec. At the instant they begin, Ellie is located 100 meters down he track in lane four, and is heading towards them in his lane at 6m/sec. After how many seconds will the runners lie in a straight line?