I think it's the first one :?
Answer:
7.071 cm
Step-by-step explanation:
Okay. So in order to solve this problem, we really have to try out each answer and divide it by 9. A is not correct, because it does not divide evenly. B works, but let's check the others. C and D do not work, but E also works as well. If you can have two answers, 504 and 882 are both exactly divisible by 9. The answers are B: 504 and E: 882.
Given:
Consider the given equation is

To find:
The values of x.
Solution:
We have,

Taking square root on both sides, we get


Adding 18 on both sides, we get


Now,
and 
and 
Therefore, the correct option is A.