Note: 9 hours 45 mins is 39/4 hours.

Recall that

Let be the total distance traveled

Let be the time for the first part of the journey

Let be the time for the second part of the journey

Let be the time for the last part of the journey

For the first third of the trip we travel :

For the second part of the journey, we also travel :

For the last part of the trip, we also travel :

Now all these times must add up to hours.

So we have:

solving for we get: