1. The problem asks to identify the property used to multiply the expression $-3(2x + 1)$. 2. The expression involves multiplying a single term outside the parentheses by each term inside the parentheses. 3. The property used here is the **distributive property**, which states that $a(b + c) = ab + ac$. 4. Applying the distributive property: $$-3(2x + 1) = -3 \times 2x + (-3) \times 1$$ 5. Simplify each multiplication: $$= -6x - 3$$ 6. This shows how the distributive property allows us to multiply a term across terms inside parentheses and then combine the results. **Final answer:** distributive