The length of one of the legs is 3, so the length of the hypotenuse is √2 times 3, or D. 6√2. Therefore, D. 6√2 is correct.
Since the triangle is a 45-45-90 triangle, we know that the hypotenuse is
√2 times longer than either leg.
Therefore, the length of the leg opposite to the angle labeled x is 312/ √2 =212.
Now, we can use the Pythagorean Theorem to solve for x.
$x^2 =
+

$x^2 =

$x =

$x =

$x =
.

$x =
.
$x =

Therefore, the value of x is 126 12 , which is equivalent to 6 √2 .
We can also check our answer by looking at the answer choices.
The only answer choice that is a multiple of √2 is (D) 6√2 .