#### Answer

$-3t$

#### Work Step by Step

Using the properties of radicals, the given expression, $
-\sqrt{(3t)^2}
,$ simplifies to
\begin{array}{l}
-(3t)
\\\\=
-3t
.\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.