Your answer will be D.
So, you have the angles 12, 9, 6, and 3. You may see that the place that 6 is makes this a non perfect square. When you have this problem simply add the number on top of it with the number that makes this problem.
For instance...

So, when finding area you must multiply the 2 lengths with each other.
So here our bottom length is also 12. Thus, we must multiply 9 and 12 together.
For instance...
