1. **State the problem:** We are given two points on a line representing the value of a building over time: $(0, 60000)$ and $(30, 0)$. We need to find the slope of the line between these points and interpret its meaning. 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. **Calculate the slope:** Substitute the points: $$m = \frac{0 - 60000}{30 - 0} = \frac{-60000}{30} = -2000$$ 4. **Interpretation:** The slope $-2000$ means the value of the building decreases by 2000 units (dollars) each year. 5. **Final sentence:** The value of the building is decreasing at a rate of 2000 per year.