1. **State the problem:** Calculate the value of $-45 - 9$. 2. **Understand the operation:** Subtracting a positive number means moving to the left on the number line. 3. **Perform the subtraction:** $$-45 - 9 = -45 + (-9)$$ 4. **Add the two negative numbers:** $$-45 + (-9) = -(45 + 9) = -54$$ 5. **Final answer:** $$\boxed{-54}$$