Need to understand on how to get the answers with to this problem

The problem ask us to evaluate each common logarithm by using a calculator. Then we have:
[tex]\begin{gathered} \log_{\placeholder{⬚}}(161)\approx2.207 \\ \log_{\placeholder{⬚}}(2,000)\approx3.301 \\ \log_{\placeholder{⬚}}(\sqrt{7})\approx0.423 \\ \log_{\placeholder{⬚}}(0.7)\approx-0.155 \end{gathered}[/tex]