The solution to this is -54.
In order to do this, you need to use Pemdas.
Pemdas:
1. P - Parentheses
2. E - Exponents (Powers and Square Roots)
3. MD - Multiplication and Division (Left to Right)
4. AS - Addition and Subtraction (Left to Right)
So, you use the distibutive property to get rid of both of the parentheses.
8 times -9 = -72
6 times -3 = -18
Then, you have the next equation of:
(-72) - (-18) = -54
So, -54 is your final answer. I hope this helps!!! :)