Let’s look at each position in the triplets separately:
Series:
BXL, DVN, FTP, ?, JPT
First letters
B → D → F → ? → J
Positions:
B(2), D(4), F(6), ?, J(10)
Pattern: +2 each time
So missing letter = 6 + 2 = 8 → H
Second letters
X → V → T → ? → P
Positions:
X(24), V(22), T(20), ?, P(16)
Pattern: −2 each time
So missing letter = 20 − 2 = 18 → R
Third letters
L → N → P → ? → T
Positions:
L(12), N(14), P(16), ?, T(20)
Pattern: +2 each time
So missing letter = 16 + 2 = 18 → R
Final missing term:
HRR
Final Answer: HRR