I understand what a logarithm is, I just can't put it to practice. When a question says "Express the following in terms of log a, log b, log c', what exactly does that mean?

Say for a question like log abc

All I see is abc to the base of 10. How do I express that?

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Then what does "Simplify the following; write as a single log" mean?

Say for log 60 - log 4

I don't think I can go log (60-4), that doesn't seem right.

Sorry for the big question, exams are coming up D: