\[\left| |x| - 9 \right| = 3\]
\[|x| - 9 = 3\]
\[|x| = 12\]
\[x = \pm 12.\]
\[|x| - 9 = - 3\]
\[|x| = 6\]
\[x = \pm 6.\]
\[Ответ:x = \pm 12;\ \ x = \pm 6.\]