It will take the car 3 hours.
If the car goes 13 miles/hour, that means that it travels 13 miles for every hour that it drives. In order to find the amount of time it takes, you just divide the distance by the speed:
[tex]\frac{39\ miles}{13\ miles/hour}=3\ hours[/tex]
Now, the question asks you to express the distance as a function of time:
d = distance, in miles
t = time, in hours
d = 13t
or
f(t) = 13t
