Chapter 9 - Section 9.1 - Quadratic Functions and Models - Exercises - Page 630: 35a

$q=-10p+400$

We have data points $(p,q)$ $(10,300)$ and $(15,250).$ An equation for the line passing through these points: $q-q_{1}=\displaystyle \frac{q_{2}-q_{1}}{p_{2}-p_{1}}(p-p_{1})$ $q=\displaystyle \frac{-50}{5}(p-10)+300$ $q=-10p+100+300$ $q=-10p+400$