Calculus: Early Transcendentals 8th Edition

$68≤ F≤86$
The interval on the Celsius scale corresponds to the temperature range. $20≤C≤30$ can be calculated as follows: Given: $C=\frac{5}{9}(F-32)$ $9C=5(F-32)$ We get, $F=\frac{9C}{5}+32$ Further, $20≤C≤30$ $\frac{9}{5}(20)≤ \frac{9}{5}C≤\frac{9}{5}(30)$ $36≤ \frac{9}{5}C≤54$ $36+32≤ \frac{9}{5}C+32≤54+32$ $68≤ \frac{9}{5}C+32≤86$ $68≤ F≤86$ Therefore, the interval on the Celsius scale corresponds to the temperature range $68≤ F≤86$.