Solving for a variable using a logarithm with a base not 10?

Question

So I have this expression: $C=Ba^{(t/D)}-k$ and I'm asked to solve for $t$ using a logarithm with base a $log_{a}$. So far, I've gotten ${((C+k)/B)} = a^{(t/D)}$. How do I move forward?

Answer 1

$$\log_aa=1$$ $$C +k=Ba^{(t/D)}$$ $$\log_a(C +k)=\log_aB +\log_aa^{(t/D)}$$