One train traveled south at 60 mph. the other traveled east at 50 mph. how far apart were the trains after 3 hours?

Let's called the train that traveled south train A, and the train that traveled east train B

After 3 hours, train A is 180 miles South
and Train B is 150 miles East

Using Pythagoras, distance between is sqrt(180^2 + 150^2)
30 sqrt(6^2 + 5^2) = 30sqrt(36 + 25) = 30sqrt 61 = 234.307 miles