1. **State the problem:** We are given that the temperature $y$ in degrees Fahrenheit is a linear function of the number of cricket chirps $x$. Two points on the graph are $(40, 50)$ and $(80, 60)$. We need to find the rate of change of temperature with respect to chirps. 2. **Identify the points:** The points given are $(x_1, y_1) = (40, 50)$ and $(x_2, y_2) = (80, 60)$. 3. **Formula for rate of change (slope):** The rate of change of a linear function is the slope $m$ given by $$m = \frac{y_2 - y_1}{x_2 - x_1}$$ 4. **Calculate the slope:** Substitute the values: $$m = \frac{60 - 50}{80 - 40} = \frac{10}{40}$$ 5. **Simplify the fraction:** $$m = \frac{\cancel{10}}{\cancel{40}} = \frac{1}{4}$$ 6. **Interpretation:** The temperature increases by $\frac{1}{4}$ degree Fahrenheit for each additional cricket chirp per minute. **Final answer:** The rate of change is $\frac{1}{4}$ degree Fahrenheit per chirp.