#### Answer

$6 \sqrt{2}$

#### Work Step by Step

Recall, $\sqrt{a}\times \sqrt{b}= \sqrt{a \times b}$. Thus, we can multiply 6 and 12 to obtain the simplified expression:
$\sqrt{6 \times 12}=\sqrt{72}$
In order to simplify a radical, we consider the factors of the number inside of the radical. If any of these factors are perfect squares, meaning that their square root is a whole number, then we can simplify the radical. We know that 36 and 2 are factors of 72. We know that 36 is a perfect square, so we simplify:
$ \sqrt{36} \sqrt{2}=6 \sqrt{2}$