Answer
12
Work Step by Step
We are given two points: (3, 36) and (7, 84). (Note, cost is the dependent variable as how much money it costs depends on the number of people.Thus, we know that people must be the independent variable). In order to find the slope, we use the following equation: $ \frac{y_{2}-y_{1}}{x_{2}-x_{1}}$. Thus, we obtain:
$\frac{84-36}{7-3}=\frac{48}{4}=12$
