#### Answer

$x=12$

#### Work Step by Step

Removing the grouping symbols and combining like terms, the value of the variable that satisfies the given expression, $
18=9-(3-x)
,$ is
\begin{array}{l}\require{cancel}
18=9-3+x
\\\\
-x=9-3-18
\\\\
-x=-12
\\\\
x=12
.\end{array}