#### Answer

$\approx 2.771$

#### Work Step by Step

We wish to find the value of the given term $\log_{3} (21)$ by using a calculator.
First, we apply the Change-of-Base Formula:
$\log_a b =\dfrac{\log b}{\log a}$
The expression can be simplified as:
$\log_{10} (21)=\dfrac{\log (21)}{\log (3)} = 2.771243749 \approx 2.771$