1. **Problem:** Calculate $7 - 9$. 2. **Formula:** Subtraction of integers. 3. **Step:** $7 - 9 = 7 + (-9)$ (subtracting 9 is adding -9). 4. **Calculation:** $7 + (-9) = -2$. 5. **Answer:** $7 - 9 = -2$. 1. **Problem:** Calculate $-6 + 10$. 2. **Formula:** Addition of integers. 3. **Step:** $-6 + 10$. 4. **Calculation:** $10 - 6 = 4$. 5. **Answer:** $-6 + 10 = 4$. 1. **Problem:** Calculate $-11 + 15$. 2. **Formula:** Addition of integers. 3. **Step:** $-11 + 15$. 4. **Calculation:** $15 - 11 = 4$. 5. **Answer:** $-11 + 15 = 4$. 1. **Problem:** Calculate $14 - 20$. 2. **Formula:** Subtraction of integers. 3. **Step:** $14 - 20 = 14 + (-20)$. 4. **Calculation:** $14 + (-20) = -6$. 5. **Answer:** $14 - 20 = -6$. 1. **Problem:** Calculate $-9 - 4$. 2. **Formula:** Subtraction of integers. 3. **Step:** $-9 - 4 = -9 + (-4)$. 4. **Calculation:** $-9 + (-4) = -13$. 5. **Answer:** $-9 - 4 = -13$. 1. **Problem:** Calculate $5 - 13$. 2. **Formula:** Subtraction of integers. 3. **Step:** $5 - 13 = 5 + (-13)$. 4. **Calculation:** $5 + (-13) = -8$. 5. **Answer:** $5 - 13 = -8$. 1. **Problem:** Calculate $-7 + 11$. 2. **Formula:** Addition of integers. 3. **Step:** $-7 + 11$. 4. **Calculation:** $11 - 7 = 4$. 5. **Answer:** $-7 + 11 = 4$. 1. **Problem:** Explain the error in the student's claim that $-3 - 4 = 1$. 2. **Formula:** Subtraction of integers. 3. **Step:** $-3 - 4 = -3 + (-4)$. 4. **Calculation:** $-3 + (-4) = -7$. 5. **Explanation:** The student incorrectly added instead of subtracting; the correct answer is $-7$. 1. **Problem:** Calculate $9 - 13 + 5$. 2. **Formula:** Perform operations from left to right. 3. **Step:** $9 - 13 = 9 + (-13) = -4$. 4. **Step:** $-4 + 5 = 1$. 5. **Answer:** $9 - 13 + 5 = 1$.