8. If the inequality about $x$
$$
|x-a|+|x-12|<6
$$

does not hold for any real number $x$, then the range of real number $a$ is . $\qquad$
8. $a \leqslant 6$ or $a \geqslant 18$.

From the given, $12-a \geqslant 6$ or $a-12 \geqslant 6$.
Solving, we get $a \leqslant 6$ or $a \geqslant 18$.