book Maths Puzzle Numerical Ability

I have several problems out there. I am really having a hard time with logarithms. Here are a few problems that are giving me some trouble.
1. Use the change of base formula a

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book Other Question

(1) write each percent as a fraction or mixed numder in the simplest form.

320%. Express the following as single logarithms, and if possible, simplify

a. Ln2x+3(Lnx-Lny)

b. 2/3[Ln(x^2-9)-Ln(x+3)]+Ln(x+y)

Convert to logarithmic notation:

x^3=-81