1. **State the problem:** Simplify the expression $24a - 12ab$. 2. **Identify common factors:** Both terms have a common factor of $12a$. 3. **Factor out the common factor:** $$24a - 12ab = 12a \times 2 - 12a \times b$$ 4. **Use the distributive property:** $$= 12a(2 - b)$$ 5. **Final answer:** The simplified form is $12a(2 - b)$. This means we took out the greatest common factor $12a$ from both terms, leaving the expression inside the parentheses.