Divide by the coefficient of x, then rationalize the denominator.
[tex]12=x\sqrt{2} \qquad\text{given}\\\\\dfrac{12}{\sqrt{2}}=x \qquad\text{divide by $\sqrt{2}$}\\\\\dfrac{12}{\sqrt{2}}\cdot\dfrac{\sqrt{2}}{\sqrt{2}}=x \qquad\text{rationalize the denominator}\\\\\boxed{x=6\sqrt{2}} \qquad\text{simplify}[/tex]
