Answer: 9/8
Explanation:
The square root of this is 9/8 because when you square 9/8, you get 81/64, and when you square root it, you get 9/8.
The easiest way tho is knowing that when you square a number and square root the square, you get the same number, cuz the square root cancels the square. Does that make sense?
Anyways hope this helped!