Can I keep the original ram of my iMac 12.1, and occupy the 2 empty slots with 2x4gb, obtain thus 12 Gb of ram total?

First I want to greet all those who want to help me in the matter I am presenting.
Then ask your understanding for the difficulties of my English (my native language is Portuguese).
So, please, write as simply as possible.

The question is:

Can I keep the original ram of my iMac 12.1, and occupy the 2 empty slots with 2x4gb, obtain thus the total ram of 12 Gb?