Couple of questions dealing with logarithms

I just need to see how they are done, so if you could work them step by step.

If logb3=.234 and logb2=.105, find logb6 .

Solve for x: log(x-5) + log(x-10)=3

438=200e.25x

A=P(1+(r/n))nt for t

4e3x=20

Thanks in advance!!