Answer:
Approximately 18.0.
Explanation:
To find x, we can use the Law of Cosines.
The Law of Cosines is the following:

Now that the c is the side we're trying to find. Thus, the c is x. Also, Angle C is the angle opposite to c (or x). a and b are the two sides next to Angle C.
Plug in x for c, 16 for a, 30 for b, and 30 for Angle C:

(Use a calculator. Make sure you're in degree mode!)