Find out the missing (?) number and letter.

To find the missing number and letter, we can analyze the patterns of the numbers and letters separately across the four quadrants of the grid.

1. Finding the Missing Number:
Let us extract the numbers from the inner triangles of the quadrants and list them in ascending order:
5, 8, 13, 20, 31, 44, ?, 80

Let us look at the differences between consecutive numbers in this sequence:
8 - 5 = 3
13 - 8 = 5
20 - 13 = 7
31 - 20 = 11
44 - 31 = 13

The differences are the consecutive prime numbers: 3, 5, 7, 11, 13. Continuing this pattern, the next differences should be the next prime numbers, which are 17 and 19:
? - 44 = 17 ⇒ ? = 44 + 17 = 61
80 - 61 = 19 (which satisfies the sequence)

Thus, the missing number is 61.

2. Finding the Missing Letter:
Let us convert the letters in the outer triangles to their corresponding numerical positions in the alphabet (A = 1, B = 2, C = 3, etc.):
- Top-Left quadrant: A = 1, C = 3
- Top-Right quadrant: C = 3, F = 6
- Bottom-Right quadrant: E = 5, I = 9
- Bottom-Left quadrant: G = 7, ?

Now, let us find the difference between the alphabetical values of the two letters in each quadrant:
- Top-Left: C - A = 3 - 1 = 2
- Top-Right: F - C = 6 - 3 = 3
- Bottom-Right: I - E = 9 - 5 = 4
- Bottom-Left: ? - G = ? - 7 = 4

Following the pattern of differences (2, 3, 4, 4), the difference for the bottom-left quadrant is 4. Therefore, the numerical value of the missing letter is:
7 + 4 = 11

The 11th letter of the alphabet is K.

Therefore, the correct option is 61 and K.