What should come in place of the question mark (?) in the given series in…

Concept

An alphanumeric series term here has a Letter-Number-Letter structure. To extend the series, convert each letter to its position in the alphabet (A=1, B=2, ..., Z=26), then track how the first-letter position, the numeral, and the second-letter position each change from one term to the next; apply that same step to get the missing term.

Application

1. Convert each term to alphabet positions and numerals: X25Z -> X=24, 25, Z=26; V23X -> V=22, 23, X=24; T21V -> T=20, 21, V=22.

2. First-letter positions across the terms: 24, 22, 20 -- each step is -2, so the next first-letter position is 20-2 = 18, which is R.

3. Numerals across the terms: 25, 23, 21 -- each step is -2, so the next numeral is 21-2 = 19.

4. Second-letter positions across the terms: 26, 24, 22 -- each step is -2, so the next second-letter position is 22-2 = 20, which is T.

5. Combining the three results (R, 19, T) gives the missing term R19T.

Cross-check

Reading the four terms position-wise -- X25Z, V23X, T21V, R19T -- all three components (first-letter position, numeral, second-letter position) fall by exactly 2 at every step, so one single uniform rule governs the whole series consistently.

So the missing term is R19T.