Concept:
Alphabetical pattern in a matrix.
Step 1: Convert letters to positions.
\[
\begin{aligned}
F=6,\ I=9,\ O=15
A=1,\ J=10,\ K=11
E=5,\ M=13,\ ?
\end{aligned}
\]
Step 2: Observe row-wise pattern.
Row 1:
\[
6 \rightarrow 9\ (+3),\quad 9 \rightarrow 15\ (+6)
\]
Row 2:
\[
1 \rightarrow 10\ (+9),\quad 10 \rightarrow 11\ (+1)
\]
Row 3:
\[
5 \rightarrow 13\ (+8),\quad 13 \rightarrow ?\ (+?)
\]
Step 3: Identify pattern.
Differences follow pattern:
\[
(+3, +6),\ (+9, +1),\ (+8, +5)
\]
Thus:
\[
13 + 5 = 18
\]
Step 4: Convert back to alphabet.
\[
18 = R
\]
Step 5: Final answer.
Thus, the missing letter is R.