X squared equals 922. The square root is a decimal which I can't use.

So I have to simplify it to a radical ... which I don't understand how to do.

If you need to siplify that radical, you should try to put all the numbers as product of prime factors.

922 = 2*461

2 and 461 are prime numbers. Then the transformation of the square root is √ (922) = √ (2*461) = (√2) (√461)

So you can use that in any expression to try to simpliy with other numbers whose prime factors include 2 and 461.