#### Answer

$3x^{2n}(4x^n-3)$

#### Work Step by Step

The greatest number that divides the numerical coefficients is 3.
The variable raised to the smallest exponent is $x^{2n}$.
Thus, the greatest common factor is $3x^{2n}$.
Factor this out to obtain:
$12x^{3n}-9x^{2n}=3x^{2n}(4x^n-3)$