Answer
$68≤ F≤86$
Work Step by Step
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 $68≤ F≤86$.
