1. The problem is to solve the expression $9) (-99) - = 6 * 9$. Since the expression is unclear, we interpret it as $-99 - x = 6 \times 9$ where $x$ is unknown. 2. Calculate the right side: $6 \times 9 = 54$. 3. Write the equation: $-99 - x = 54$. 4. To isolate $x$, add $99$ to both sides: $$-99 - x + 99 = 54 + 99$$ $$\cancel{-99} - x + \cancel{99} = 153$$ 5. Simplify: $$-x = 153$$ 6. Multiply both sides by $-1$ to solve for $x$: $$\cancel{-1} \times -x = 153 \times \cancel{-1}$$ $$x = -153$$ 7. Final answer: $x = -153$.