The letter in the first row form a series C, D, E (a series of consecutive letters).
The letters in the second row from a series I, K, M (a series of alternate letters).
Similarly, the letters in the third row will form the series D, G, J (a series in which each letter is three steps ahead of the previous one).
So, the missing letter is G.
Also, the number in the second column is equal to the product of the numbers in the first and third columns.
So, missing number is (4 x 7) i.e. 28.
Thus, the answer is 28G.