#### Answer

$ 24c^{7}$

#### Work Step by Step

$-1/3 \times -6 \times \sqrt {18c^{5} \times 8 c^{9}} =2 \sqrt {144 c^{14}}$
We now separate the number and the variable into two separate square roots:
$ 2 \sqrt {144} \times \sqrt {c^{14}} =2\sqrt {144} \times c^{7}$
We see if any of the factors of a radical are perfect squares (meaning that their square root will be an integer) to see if the radical is in its most simplified form. Because 144 is a perfect square, we know that we can simplify:
$2 \sqrt {144} \times c^{7}= 24c^{7}$