The closest correct answer from the options provided is:
Multiply 6 x 3 for the numbers; then add 2 + 4 for the exponent on x.
This option correctly reflects that you multiply the coefficients (6 and 3) and add the exponents of \( x \) since you're combining like terms with the same base \( x \).
So the expression simplifies to: \[ (6 \cdot 3)x^{4+2} = 18x^6 \]