Question

I don’t know how to do it

Answer 1

3.75 miles

Explanation:

You want to have a formula for the "distance to the destination" as a function of the time, let's call it d(t). Given is that d(0)=60, and you are interested in d(2.5).

d(t) = 60 - 22.5t will do the trick.

d(2.5) = 60 - 22.5*2.5 = 3.75