Two trains leave the station at the same time, one heading west and the other east. the westbound train travels 12 miles per hour slower than the eastbound train. if the two trains are 680 miles apart after 4 hours, what is the rate of the westbound train?

Allow the westbound train to be "w" and the eastbound train to be "e". We can make the following equation:

4 (e + (e - 12)) = 680
4 (2e + 12) = 680
8e - 48 = 680
8e = 728
e = 91 mph

e - 12 = w
91 - 12 = w
79 = w

Therefore, the westbound train travels at 79 miles per hour.