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

For every hour more that the babysitter works, the babysitter earns more money. Thus, we know that the slope is positive. We are given two points: (1,9) and (4, 36). In order to find the slope, we use the following equation: $\frac{y_{2}-y_{1}}{x_{2}-x_{1}}$. Thus, we obtain: $\frac{36-9}{4-1}=\frac{27}{3}=9$