I don't really understand your wording of the question, but this is what I did: I made a key (like in proportions) with the hours on top and the distance as the denominator. I put 3 over 120 and I did the same thing with the 200 miles, but I substituted the constant speed with "x". Then I cross multiplied and ended up with the equation "120x=600". After that, just divide by 120 and get and answer of 5 hours.
