1. **State the problem:** We are given points on a line: (3,20), (7,16), (11,12), and (15,8). We need to find the slope of the line passing through these points. 2. **Formula for slope:** The slope $m$ between two points $(x_1,y_1)$ and $(x_2,y_2)$ is given by: $$m = \frac{y_2 - y_1}{x_2 - x_1}$$ 3. **Choose two points:** Let's use the first two points $(3,20)$ and $(7,16)$. 4. **Calculate the slope:** $$m = \frac{16 - 20}{7 - 3} = \frac{-4}{4}$$ 5. **Simplify the fraction:** $$m = \frac{\cancel{ -4}}{\cancel{4}} = -1$$ 6. **Verify with another pair:** Using points $(7,16)$ and $(11,12)$: $$m = \frac{12 - 16}{11 - 7} = \frac{-4}{4} = -1$$ 7. **Conclusion:** The slope of the line is $-1$.