The hypotenuse must be longer than either of the legs. So the differnce between the hypotenuse and the middle leg is 1.
So hypotenuse = (x+1)2 = x2 + s2, where s is the length of the shortest leg.
Thus, x2 + 2x + 1 = x2 + s2.
So, 2x + 1 = s2 = 32 = 9.
2x + 1 = 9
Subtracting 1 from both sides,
2x = 8
Divide both sides by 2:
x = 4.
The hypotenuse must be x +1 = 4 + 1 = 5.
The given units are always miles.