Two trains left the station at the same time, one heading due east at 40 miles per hour and the other heading due west at 50 miles per hour.

how far apart were they after 4 hours?

don't tell me the answer just tell me how to do it

Well in one hour the train going east is going 40 mph. In 4 hours the train is 160miles because 40x4=160 so it's 160 miles away from the satiation, and train that's going west is going 50 mph. In 4 hours the train is 200 miles from the satiation. 50x4=200 if you add 160 and 200 you get the distance between both trains