## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Each tick mark on the x-axis represents $0.25$ units.
Slope is the rise over run (or rise divided by the run). Having a slope of $-\dfrac{2}{3}$ means that the rise is $-2$ and the run is $3$. The two points have unknown x-coordinates but their y-coordinates are known: $(x_1, 3)$ and $(x_2, 2)$ The rise between the two points is $=2-3=-1$ The run is represented by $x_2-x_1$. Thus, the slope is given by: $=\dfrac{\text{rise}}{\text{run}}=\dfrac{-1}{x_2-x_1}$ The slope is $-\dfrac{2}{3}$. Note that $\dfrac{-1}{1.5}=-\dfrac{1}{1.5}=-\dfrac{2}{3}$. So you can have: $\dfrac{-1}{x_2-x_1}=\dfrac{-1}{1.5}$ This means that $x_2-x_1=1.5$ Note that there are six vertical tick marks from $(x_1, 3)$ to $(x_2, 2)$ These vertical tick marks must represent 1.5 units. Divide $1.5$ units by 6 tick marks to have: $=\dfrac{1.5\text{ units}}{6\text{ tick marks}}=0.25$ units per tick mark.