(|3.6| - |-8.1|) * |-9|

First, calculate the absolute values:
|3.6| = 3.6
|-8.1| = 8.1

Then, subtract the absolute values:
|3.6 - 8.1| = 8.1 - 3.6 = 4.5

Now, multiply by |-9|:
4.5 * 9 = 40.5

So, the solution is 40.5.