1. **State the problem:** We are given two points on a line representing the distance traveled by a motorist over time: (3, 120) and (6, 240). 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: $$m = \frac{y_2 - y_1}{x_2 - x_1}$$ This formula calculates the rate of change of distance with respect to time. 3. **Calculate the slope:** $$m = \frac{240 - 120}{6 - 3} = \frac{120}{3} = 40$$ 4. **Interpretation:** The slope $40$ means the motorist travels 40 miles per hour. This is the rate of change of distance with respect to time. 5. **Final sentence:** The motorist was traveling at a rate of 40 miles per hour.