1. Identify the function: f(x) = 3x
2. Apply the power rule of differentiation. The power rule states that for a function of the form f(x) = ax^n, the derivative is f'(x) = anx^{n-1}.
3. In this case, a = 3 and n = 1. Thus, the derivative of 3x is 3 \cdot 1 \cdot x^{1-1} = 3 \cdot x^0 = 3.
Therefore, the derivative of 3x is 3.