1. State the problem: Simplify $$6x - [5x(-2x + 6)] + 3x^2$$. 2. First, distribute inside the brackets: $$5x \times (-2x) = -10x^2$$ and $$5x \times 6 = 30x$$. 3. This gives: $$6x - (-10x^2 + 30x) + 3x^2$$. 4. Remove the brackets carefully, remembering the minus sign before the bracket: $$6x + 10x^2 - 30x + 3x^2$$. 5. Combine like terms: - Combine $$10x^2$$ and $$3x^2$$ to get $$13x^2$$. - Combine $$6x$$ and $$-30x$$ to get $$-24x$$. 6. Final simplified expression is $$13x^2 - 24x$$.