We need to find how many trips she will have to make to cover a total of 24 kilometers.
We know that she covered 15 kilometers by making 5 trips. Thus, the number of kilometers made on each trip is:
Then, she made 3 kilometers on 1 trip (unit rate).
Now, to cover 24 kilometers, she needs to make 8 trips, because:
Thus:
Answer: She will have to make 8 trips.