Answer:
 4.58 miles
Explanation:
The Pythagorean theorem is used to answer such questions. It tells you the relation between the side lengths is ...
 AC² = AB² +BC²
In miles, ...
 5² = AB² + 2² . . . . . . . fill in the given numbers
 25 -4 = AB² . . . . . . . . subtract 2²
 √21 = AB ≈ 4.58 . . . . . take the square root
The distance in miles from A to B is about 4.58.