#### Answer

$t^9$

#### Work Step by Step

Using the properties of radicals, the given expression, $
\sqrt[]{t^{18}}
,$ simplifies to
\begin{array}{l}
\sqrt[]{(t^9)^{2}}
\\\\=
t^9
.\end{array}
Note that it is assumed that no radicand was formed by raising negative quantities to even powers. Thus, absolute value bars are not necessary.