algebra precalculus - train is traveling from point A to point B, the distance between these two points is $329$ miles. The total time it takes for the train to travel...

A train is traveling from point A to point B, the distance between these two points is $329$ miles. The total time it takes for the train to travel between point A and B is $7$ hours. If for the first $74$ miles the train travels at a speed of $14$mph slower than its speed during the last $255$ miles, what is the trains speed during the last $255$ miles?

I know $speed=\frac{distance}{time}$, if we represent $x$ as the trains speed during the last $255$ miles then $x-14$ represents the speed during the first $74$ miles, and the average speed throughout the entire speed is $speed=\frac{329}{7}$, this is $47$mph.
Now I don't know how to find the speed during the last $255$ miles?

I don't want the answer I just need help with figuring it out.

Answer

You can solve $$\dfrac{74}{(x-14)}+\dfrac{255}x=7$$