#### Answer

6$\sqrt 3$

#### Work Step by Step

The Pythagorean Theorem says that $(leg_{1}) ^{2}$+$(leg_{2})^{2}$=$hypotenuse^{2}$.
This formula is more commonly referred to as $a^{2}$+$b^{2}$=$c^{2}$
You are given the lengths of one leg as 6 and the length of the hypotenuse as 12. Substitute 6 in for a and 12 in for c.
$a^{2}$+$b^{2}$=$c^{2}$
$6^{2}$+$b^{2}$=$12^{2}$
36+$b^{2}$=144
Subtract 36 from both sides.
$b^{2}$=108
Take the square root of both sides to find the length of the missing side.
b=6$\sqrt 3$