1. **Problem statement:** Simplify the expression $$9x - (3 - 3x)$$ by first removing the parentheses and then combining like terms. 2. **Formula and rules:** When removing parentheses preceded by a minus sign, change the signs of the terms inside the parentheses. 3. **Step-by-step simplification:** $$9x - (3 - 3x) = 9x - 3 + 3x$$ 4. **Combine like terms:** $$9x + 3x - 3 = 12x - 3$$ 5. **Final answer:** $$12x - 3$$ This means the simplified expression is $12x - 3$.