Puzzle: Which letter replaces the question mark?

Question

Answer 1

Answer: M

Explanation: Working in rows, add together the numerical values of the left and right hand letters to give the numerical value of the central letter.

Answer 2

May be M is the answer

Answer 3

The middle alphabet is sum of the position of its predecessor and successor alphabet's position.
E M H : position of E=5 , position of M= 13 ,position of H=8 then, (5+8)=13

N O A: position of N=14 , position of O=15 , position of A=1 , (14+1)=15

I .... D: position of I=9 , position of ....= ..... , position of D=4 , now (9+4)=13

13th position alphabet is M
so M is the answer