We have

And we want

Another way to read it is

It should be clear that the solution is 
Answer:
I believe it's 36
Step-by-step explanation:
Also is this a test lol?
Answer:
75%
Step-by-step explanation:
$16 = 100%
$12 = ?%
?% = (12 * 100) / 16
?%= 75%
That would be D. The first two would be fight (I think) except they don't include turning the calculator on. C is just plain wrong. D has all the right keystrokes.