Answer:
15 miles.
Explanation:
Since this is a right triangle, you have to follow the Pythagorean Theorem to solve this problem. The 2 sides-12 and 9 miles- are the known sides, and we have to find what is the value of c. The first Pythagorean Triplet(It is the pythagorean theorem, it just the triplets) is 3,4,5. If you multiple each of the numbers of any number, you will get another triplet. So, if you multiple 3,4, and 5 by 3, you will get 9, 12, and 15.