Check multipliers step wise:

From 12 → 18 : multiply by $1.5$ From 18 → 36 : multiply by $2$ From 36 → 90 : multiply by $2.5$

There is a very clear increasing pattern in multipliers:

$0.5$ → $1$ → $1.5$ → $2$ → $2.5$

So: $X \times 1 = 12$ $X = 12$

Then check one more back:

Before $\times 1$ ($X \rightarrow 12$) must be $\times 0.5$ ($24 \rightarrow X$)

$24 \times 0.5 = 12$ → matches perfectly.

Option B is correct: 12 exactly fits the multiplier logic.