Which one will replace the question mark ?

Concept: Each group in this figure follows one fixed arithmetic rule linking its three numbers — top, middle, and bottom. Once the rule is confirmed using groups where all three values are known, the same rule is applied to solve for the missing value in an incomplete group.

Application: Reading the pattern from the two complete groups and applying it to the third:

1. Group 1 has top = 3, middle = 15, bottom = 27. Testing (middle × 2) − top: (15 × 2) − 3 = 27, which equals the bottom value.

2. Group 2 has top = 6, middle = 31, bottom = 56. Testing the same rule: (31 × 2) − 6 = 56, which again equals the bottom value — confirming the rule holds across groups.

3. Group 3 has top = 9, bottom = 81, and an unknown middle value, x. Applying the same rule: (x × 2) − 9 = 81.

4. Solving: 2x = 81 + 9 = 90, so x = 90 ÷ 2 = 45.

Cross-check: Substituting x = 45 back into the rule gives (45 × 2) − 9 = 90 − 9 = 81, matching the bottom value shown for the third group, so 45 is confirmed as the missing number.