Answer:
The pythagoras's theorem is the relation between the sides of a right-angles triangle, it shows that the square of the hypotenuse of the triangle will be equal to the sum of squares of the remaining sides
hypotenuse² = perpendicular² + base²
replacing the variables with the sides of the given triangle:
x² = 15² + 8²
x² = 225 + 64
x² = 289
x = √289
x = 17 mi