Find all possible positive integer $n$ such that $3^{n-1} + 5^{n-1} \mid 3^n + 5^n $ 
Find all possible positive integers $n$ such that $3^{n-1} + 5^{n-1} \mid 3^n + 5^n $.

I don't know how to start with. Any hint or full solution will be helpful.   

Hint: $A:=3^{n-1}+5^{n-1}$, and $B:=3^n+5^n$. 
Compare $3A$ and $5A$ to $B$ to get the possible values of the integer $B/A$.
