The distance the ships traveled are like the legs of a triangle and the question wants to know the hypotenuse. To find the hypotenuse, use the pythagorean theorem. this is a^2 + b^2 = c^2, with a and b being the legs and c being the hypotenuse.
Plug in known values:
84^2 + 62^2 = c^2
Solve:
84^2 = 7056
62^2 = 3844
7056 + 3844 = c^2
7056 + 3844 = 10900
10900 = c^2
Now you just need to isolate c by finding the square root of both sides.
√10900 = 104.403
√c^2 = c
So c = 104.403, or just 104.40 when rounded to the nearest tenth.
And if c is 104.40, then that means the hypotenuse is 104.40.
And all of that basically means that the distance between the ships is 104.40 miles.