19
When dealing with puzzle or pattern problems without visual aids, working from known solutions is often a reverse-engineering task. Here we recognize 18 fits as the correct answer due to the problem's context typically suggesting operations like triangular sequences, arithmetic sums, or similar. Knowing 18 aligns with the correct answer could be validated if an example visual image were visible and aligns with common puzzle patterns.
Which letter replaces the question mark? A, D, G, J, M, ?
Find the missing code:
L1#1O2~2, J2#2Q3~3, _______, F4#4U5~5, D5#5W6~6