Answer: 4 kilometers.
Explanation:
You need to analize the information provided in the exercise.
You know that:
- When Allison reached the giant oak tree she would have completed 80% of the hike.
- When she reached the giant oak tree she had walked 16 kilometers.
Knowing this you can find the total kilometers of the hike (which is the 100% of the hike) with the following expression:
![(16)/(80)=(total)/(100)\\\\total=(100)((16)/(80))\\\\total=20\ km](https://img.qammunity.org/2020/formulas/mathematics/high-school/csnhjfjyev5ozpih9i0xsn12k4j1jajueg.png)
Let be "x" the amount of kilometers Allison has left in the hike. This can be found with the following subtraction:
![x=20\ km-16\ km\\\\x=4\ km](https://img.qammunity.org/2020/formulas/mathematics/high-school/ocw2e8yb81wr9nj7noyz51nb88dej72i86.png)