Answer
$3 \sqrt{2}$
Work Step by Step
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 4 and 2 are factors of 8. We know that 4 is a perfect square, so we simplify:
$3/2 \sqrt{4} \sqrt{2}=3 \sqrt{2}$
