Two trains leave the station at the same time, one heading east and the other west. The westbound train travels 12 miles per hour slower than the eastbound train. If the two trains are 640 miles apart after 4 hours, what is the rate of the westbound train? No Rounding.
since distance = speed * time, if the slower train's speed is x mi/hr, then
4(x + x+12) = 640