## Algebra 1: Common Core (15th Edition)

We are given two points: (1,200) and (3,80). (Note, time is the independent variable as how far away the car is from its destination does not change what time it is. This makes where the car is the dependent variable). In order to find the slope, we use the following equation: $\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$. Thus, we obtain: $\frac{200-80}{1-3}=\frac{120}{-2}=-60$