Chapter 1 - Linear Functions - 1.2 Linear Functions and Applications - 1.2 Exercises - Page 25: 47

Solution: $-40$ $-40^\circ F=-40^\circ C$

To find the temperature at which the Celsius ($C)$ and Fahrenheit ($F)$temperatures are numerically equal. Let $F=C=x$ The relation between the Fahrenheit and the Celsius scale is given by the equation: $F=\frac{9}{5}C+32$. When $F=C=x,$ $x=\frac{9}{5}x+32\implies x=-40$