This is an awkward question to me, it was not covered in class.
Suppose:
$$\begin{align*} \log_b 2 &= A, \\ \log_b 3 &= B, \\ \log_b 5 &= C. \end{align*} $$
Then, use the change-of-base formula to evaluate
$$\log_{b^2} 5$$
and
$$\log_{\sqrt b} 2 .$$
As an example answer, we're given $\log_3 b$ becomes $1/B$.
Hopefully someone understands where they're coming from.