In each of the following questions, a group of three numbers/symbols is given in each option. Identify the group that does NOT follow the same pattern as the others.

Correct — D.
Rule: each number is its letter's alphabet position, and the letters step back 3.

M13 : J10 : G7 → M = 13, J = 10, G = 7
Z26 : W23 : T20 → Z = 26, W = 23, T = 20
D4 : A1 : X24 → D = 4, A = 1, X = 24 (back 3 from A wraps to X)

H8 : E6 : B4 → E is 5th and B is 2nd, so 6 and 4 are wrong → option (d).

Why the others are wrong

• (a)
  M13 : J10 : G7 — M13 : J10 : G7 pairs each letter with its own position, 13, 10, 7, and steps back three letters each time. It follows the rule.
• (b)
  Z26 : W23 : T20 — Z26 : W23 : T20 gives Z, W and T their true positions and steps back three letters twice. It follows the rule.
• (c)
  D4 : A1 : X24 — D4 : A1 : X24 looks broken because 1 jumps to 24, but X really is the 24th letter: stepping back three from A wraps round to X.

Letter-number groups hide two rules at once: how the number relates to its letter, and how the letters move from term to term. Check both in every option.

In the regular groups the number is the letter's alphabet position and the letters step back three. H8 : E6 : B4 keeps the letter step, H → E → B, but its numbers fall by 2, so E and B carry the wrong numbers.

Key facts

• B is the 2nd letter, E the 5th, H the 8th.
• Counting back three from A passes Z and Y and lands on X, the 24th letter.
• Positions used here: D4, G7, J10, M13, T20, W23, X24, Z26.

Common traps

• Marking D4 : A1 : X24 odd because 24 does not fall by 3 from 1, when the wrap-around keeps it regular
• Checking only the letter step, which H → E → B passes, and never testing the numbers against the letters

No directly related past PYQ was found.