There isn’t a valid answer to the question.

Ignore the numbers, and just think about this:
Is there a number that you can add 2 to, that would equal the same about as if you subtracted 2 from it?
The answer is no.

So the person, who is pretending to be smart, just did a bunch of fake math.
Also √4 = 2, so the “answer” they have is just them trying to re-write the question x + 2 = x - 2.