Use properties of logarithms with the given approximations to evaluate the expression.

Use $\log _{b} 2=0.693$ and/or $\log _{b} 9=2.197$ to find $\log _{b} 18$.

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Answer

Final Answer: $\boxed{2.89}$

Steps

Step 1 ：We are given that $\log_b 2 = 0.693$ and $\log_b 9 = 2.197$

Step 2 ：We can express $\log_b 18$ as $\log_b 2 + \log_b 9$ due to the property of logarithms that states $\log_b (xy) = \log_b x + \log_b y$

Step 3 ：Substituting the given values, we get $\log_b 18 = 0.693 + 2.197$

Step 4 ：Adding these values, we find that $\log_b 18 = 2.89$

Step 5 ：Final Answer: $\boxed{2.89}$