1. **State the problem:** Simplify the expression $-(-18)$. 2. **Understand the rule:** The negative of a negative number is a positive number. This is because multiplying two negative signs results in a positive. 3. **Apply the rule:** $$-(-18) = +18$$ 4. **Conclusion:** The simplified value of $-(-18)$ is $18$. Therefore, the correct answer is **18**.