1. **State the problem:** Simplify the expression $-15 - (-12 - 6)$.
2. **Recall the rule:** Subtracting a negative number is the same as adding its positive counterpart.
3. **Simplify inside the parentheses:**
$$-12 - 6 = -18$$
4. **Rewrite the expression:**
$$-15 - (-18)$$
5. **Apply the subtraction of a negative:**
$$-15 + 18$$
6. **Calculate the sum:**
$$-15 + 18 = 3$$
**Final answer:** $3$
Simplify Expression Ca7A44
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