To find \((f - g)(x)\), we need to calculate:
\[ (f - g)(x) = f(x) - g(x) \]
Given:
\[ f(x) = 3x - 2 \] \[ g(x) = 2x + 1 \]
Now, compute \(f(x) - g(x)\):
\[ f(x) - g(x) = (3x - 2) - (2x + 1) \]
Distributing the negative sign:
\[ = 3x - 2 - 2x - 1 \]
Now combine like terms:
\[ = (3x - 2x) + (-2 - 1) \] \[ = x - 3 \]
Thus, \((f - g)(x) = x - 3\).
The answer is \(\text{D. } x - 3\).