(1) $Z=\frac{P V T}{R}$ : This is incorrect because the units on both sides don't match.
(2) $Z=\frac{n R T}{P V}$ : This is incorrect because it's the inverse of the correct formula.
(3) $Z=\frac{P V}{n R T}$ : This is the correct formula for the compressibility factor.
(4) $Z=\frac{(P V)}{R T} \times n$ : This is also incorrect because it doesn't match the standard formula for $Z$.