Find the odd alphanumeric triplet (number equals first-letter position): Select the item that breaks the “number = alphabet index of first letter” rule or format.

Introduction / Context:
Alphanumeric classification commonly ties digits to alphabet indices (A=1, B=2, …). A consistent mapping across options provides a simple test: if the trailing number equals the index of the first letter, items conform; otherwise they deviate.

Given Data / Assumptions:

• G=7 → GT7 conforms.
• I=9 → IR9 conforms.
• C=3 → CX3 conforms.
• J=10 → JP10 also conforms numerically, but it is the only two-digit numeral while others use a single digit.

Concept / Approach:
When all items satisfy the base mapping, we look for a secondary, consistent presentational pattern. Three items use single-digit numerals (1–9). One item requires two digits (10), visibly breaking the shared format, which is a legitimate odd-one-out criterion in symbol puzzles.

Step-by-Step Solution:

Verification / Alternative check:
Confirm that second letters (T, R, X, P) have no consistent link to the number, so the only uniform presentational difference is digit count.

Why Other Options Are Wrong:
They visually match the 1-digit formatting of the set.

Common Pitfalls:
Do not try to force secondary mappings (e.g., to the second letter); those are not consistent across items.

Final Answer:
JP10