Find the unknown side length, x. write your answer in simplest radical form.
a. 14
b. 18
c. 2 square root 119
d. 14 square root 17

The unknown side length is so unknown that we don't even know what it's
a side of, or how many other sides there are, or what is the length of any of
those others, or what the relationship might be between the side length we're
concerned with and the length of any of those others that we don't care about. 

The question involves too many unknowns.  It's a lot like asking:

"Find the unknown person's height, H.  Write your answer in feet and inches."
Hint: The unknown person attended the Super Bowl in 2013.  Here's an aerial
photograph of the stadium during half-time.

Ais the correct answer