1. **Problem:** Find the greatest common factor (GCF) of 8 and 18. 2. **Formula and Rules:** The GCF of two numbers is the largest number that divides both without leaving a remainder. 3. **Step 1:** List factors of 8: 1, 2, 4, 8. 4. **Step 2:** List factors of 18: 1, 2, 3, 6, 9, 18. 5. **Step 3:** Common factors: 1, 2. 6. **Step 4:** Greatest common factor is 2. --- 1. **Problem:** Find the GCF of 10 and 16. 2. **Step 1:** Factors of 10: 1, 2, 5, 10. 3. **Step 2:** Factors of 16: 1, 2, 4, 8, 16. 4. **Step 3:** Common factors: 1, 2. 5. **Step 4:** GCF is 2. --- 1. **Problem:** Find the GCF of 9 and 12. 2. **Step 1:** Factors of 9: 1, 3, 9. 3. **Step 2:** Factors of 12: 1, 2, 3, 4, 6, 12. 4. **Step 3:** Common factors: 1, 3. 5. **Step 4:** GCF is 3. --- 1. **Problem:** Find the GCF of 20 and 24. 2. **Step 1:** Factors of 20: 1, 2, 4, 5, 10, 20. 3. **Step 2:** Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24. 4. **Step 3:** Common factors: 1, 2, 4. 5. **Step 4:** GCF is 4. **Final answers:** - GCF(8,18) = 2 - GCF(10,16) = 2 - GCF(9,12) = 3 - GCF(20,24) = 4