#### Answer

$\frac{6}{x(2x+1)}$

#### Work Step by Step

By inspection, we see that the LCM of the denominators is $x(2x+1)$. Therefore, we create a common denominator using this LCM and obtain:
$\frac{6}{x}-\frac{12}{2x+1}$
=$\frac{6(2x+1)-12(x)}{x(2x+1)}$
=$\frac{12x-12x+6}{x(2x+1)}$
=$\frac{6}{x(2x+1)}$