Which one will replace the question mark ?

Concept: In this type of figure-based number series, the three numbers at the tips of each figure are combined by one fixed arithmetic operation to give the number at the base of that figure. The same operation applies to every figure in the set, so it can be discovered from the figures that are already complete and then used to fill in the missing base value.

Application:

1. First figure: 12 + 18 + 30 = 60, and 60 ÷ 10 = 6, which matches the given base value 6.

2. Second figure: 16 + 24 + 40 = 80, and 80 ÷ 10 = 8, which matches the given base value 8.

3. Both complete figures confirm the same rule: sum of the three top numbers ÷ 10 = base number.

4. Third figure: 45 + 18 + 27 = 90.

5. Applying the confirmed rule: 90 ÷ 10 = 9.

Cross-check: The rule sum ÷ 10 works exactly, with no rounding or adjustment, for both given figures, so it is a reliable pattern rather than a coincidence in a single figure, and can be applied to the incomplete figure with confidence.

Result: The missing number is 9.