1. Is there such number N that 7 divided N^2=3?
Isnt it just root of 7/3?
2. x^2 + y^2 = z^2. Prove xyz is a multiple of 60
Not sure what to do here, and where to get the xyz term from
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.