Sativa -Train A is going 40 mph and Train B is going 52 mph.Here is a very important equation for this problem:distance = rate x time, or in math symbolsd=r*tRearranging this by solving for time:d/r = tIn this problem, both trains travel over the same time, but different distances. So here is how to set up the equation:, where "s" equals the speed of Train ANow, simply solve for s ... I'll leave the math for you!Once you know s, then train A is going 12 mph less:Train A:speed equals s - 12Hope that helps