Answer:

Explanation:
Using the Pythagorean Theorem, if you take 8 and square it, you get 64.
You then take 5 and square it giving you 25.
add the 64 and 25 to get you 89 = x squared.
Then take the square roots of x. (Keep in mind, what you do to one side must be done to the other.)
Because 89 is not a perfect square, you can it it as the square root of 89.