1)

I assume you mean 7 divided by n^2 = 3

If you're dealing with divisibility in number theory, I think the question may be asking if there is an integer which divides 7 giving the quotient 3. This would mean that 7 would have 3 as a factor. 7, being prime, has no factors.

However the root of 7/3 does does yield a quotient of 3. The number does exist (root of 7/3), but it is not an integer.