1. **Problem:** Find the slope of the function $P = 12 - Q$ at all values of $Q$. 2. **Formula:** The slope of a function is given by its derivative with respect to the independent variable. Here, $P$ is a function of $Q$, so slope $= \frac{dP}{dQ}$. 3. **Calculation:** $$\frac{dP}{dQ} = \frac{d}{dQ}(12 - Q) = 0 - 1 = -1$$ 4. **Explanation:** The slope is constant and equals $-1$ for all values of $Q$. This means the function decreases at a constant rate as $Q$ increases. **Final answer:** The slope of the function $P = 12 - Q$ is $-1$ at all values of $Q$.