To obtain Drian's final bill, the following steps are necessary:
Step 1: Find the separate amounts Drian paid as tax, and as tip, as shown below:
- Tax = 6% of $ 150, which is:

- Tip = 15% of $ 150, which is:

Step 2: Add the separate amounts of the tax and tip to the initial bill given to Drian in order to obtain his final bill, as follows:

Since:
Initital bill = $ 150
Tax = $ 9
Tip = $ 22.5
Therefore:

Therefore, Drian's final bill is $ 181.5