1. **State the problem:** Simplify the expression $3u - 10(10u - 10)$. 2. **Apply the distributive property:** Multiply $-10$ by each term inside the parentheses: $$3u - 10 \times 10u + 10 \times 10$$ 3. **Calculate the products:** $$3u - 100u + 100$$ 4. **Combine like terms:** Combine $3u$ and $-100u$: $$\cancel{3u} - \cancel{100u} = -97u$$ So the expression becomes: $$-97u + 100$$ 5. **Final answer:** $$\boxed{-97u + 100}$$