The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?
![which letter replaces the question mark which letter replaces the question mark](https://www.briddles.com/images/riddles/which-letter-replaces-the-question-mark-1063.png)
The missing letter is Q.
If you add the three numbers on each square, the value corresponds to the equivalent alphabet in the center. For example 6 + 4 + 4 = 14 and N is the 14th letter. Similarly 14 + 2 + 1 = 17 or the letter Q.