1. **State the problem:** We are asked to evaluate expressions where we start with a negative number and then add or subtract another number, making the result more negative. This is called "Case 3". 2. **Formula and rule:** Adding a negative number is the same as subtracting a positive number. For example, $a + (-b) = a - b$. 3. **Evaluate each expression step-by-step:** - $1.$ $-2 - 3 = -2 + (-3) = -5$ - $2.$ $-1 - 6 = -1 + (-6) = -7$ - $3.$ $-4 + (-4) = -8$ - $4.$ $-9 + (-2) = -11$ - $5.$ $-8 - 4 = -8 + (-4) = -12$ - $6.$ $-4 + (-6) = -10$ - $7.$ $-1 + (-8) = -9$ - $8.$ $-15 - 2 = -15 + (-2) = -17$ - $9.$ $-9 + (-11) = -20$ - $10.$ $-5 + (-14) = -19$ - $11.$ $-20 - 5 = -20 + (-5) = -25$ - $12.$ $-13 - 3 = -13 + (-3) = -16$ - $13.$ $-12 + (-3) = -15$ - $14.$ $-16 - 2 = -16 + (-2) = -18$ - $15.$ $-50 - 50 = -50 + (-50) = -100$ Each step shows how adding a negative number is the same as subtracting a positive number, making the total more negative. **Final answers:** $-5, -7, -8, -11, -12, -10, -9, -17, -20, -19, -25, -16, -15, -18, -100$