Step 1: Express 99 suitably.
\[
\log_{10}99 = \log_{10}(100 - 1)
\]
Step 2: Use logarithmic approximation.
For small \(x\),
\[
\log(1-x) \approx -x \log e
\]
Thus,
\[
\log_{10}99 = \log_{10}100 + \log_{10}\left(1-\frac{1}{100}\right)
\]
Step 3: Substitute values.
\[
= 2 - \frac{1}{100}\log_{10}e
\]
\[
= 2 - \frac{1}{100}(0.4343)
\]
Step 4: Final calculation.
\[
\log_{10}99 \approx 2 - 0.004343 = 1.9957
\]