This is a d=rt problem. We are going to need to identify r (speed) and t (time) in order to figure it out.

The diagram tells us that the distance from A to B is 50x, d=50x and the problem tells us that the speed from A to B was 50, r=50. Since d=rt=50x, x must be the time it took to get from A to B.
So, from A to B:
r=50

t=x

d=50x

Now, we need to figure out an expression for the distance from B to C. The problem tells us that the speed from B to C was 40, r=40. We need to figure out what the time was from B to C (or an expression for it). 
The problem tells us that the overall time for the entire trip was 5 hours and we've just figured out that the first part of the trip, from A to B, took 'x' hours. What is an expression you can write for the time the trip took from B to C?

Once you've got an expression from B to C, you are able to write an equation with x in it (an expression for the entire trip that will be equal to 215, the distance of the whole trip).

Let me know if this helps, Mrs. Tabitha