1. **State the problem:** Factor the expression $15k - 18$ using 3 as the common factor. 2. **Recall the factoring formula:** When factoring out a common factor $a$ from terms $ax + ay$, the expression becomes $a(x + y)$. 3. **Identify the common factor:** Both $15k$ and $18$ are divisible by 3. 4. **Divide each term by 3:** $$15k \div 3 = 5k$$ $$18 \div 3 = 6$$ 5. **Write the factored form:** $$15k - 18 = 3(5k - 6)$$ 6. **Explanation:** We took out the common factor 3, then divided each term by 3 to get the terms inside the parentheses. **Final answer:** $$15k - 18 = 3(5k - 6)$$