Answer:
The car travels 64 miles per hour.
Explanation:
The problem is asking for the ratio between distance and time, and that it's the definition of speed, so we use:

Now, we need to find the ratio in miles and hours, that means we have to transform 15 minutes into hours to know the total time in hours.
We know that 1 hours is 60 minutes, applying this ratio, we have:

So, the total time the car travels is 4.25 hours.
Now, we calculate the ratio:

Therefore, the car travels 64 miles per hour.