The missing side of the right triangle round to the nearest hundredth is;
x = 12.21 units.
In Mathematics and Geometry, Pythagorean's theorem is an Euclidean postulate that can be modeled or represented by the following mathematical equation:

Where:
- a is the opposite side of a right-angled triangle.
- b is the adjacent side of a right-angled triangle.
- c is the hypotenuse of a right-angled triangle.
In order to determine the length of x, we would have to apply Pythagorean's theorem as follows;

x = 12.2066 ≈ 12.21 units.