The answer is 2.5 miles.
To answer this question, you need to use the Pythagoras theorem, which is: a square + b square = c square.
A is 2.1 miles. 2.1 squared is 4.41.
B is 1.3 miles. 1.3 squared is 1.69.
If you add those two, it becomes 6.1.
The square root of that (you’ll need a calculator) is 2.4698... , which, rounded to the nearest tenth of a mile is 2.5