C'est quoi la question?
Yes you've got to simplify the expression and you will find all the n's evenyuallu cancel out. I got 216 as the value for A.
Start by writing 8 as 2^3 and 4 as 2^2.
Then use your index laws and factorising.
A few hints: (2^3)^(n+1) = 2^(3n+3) = 2^(3n) x 2^3.
Give it a try....I'll check in again later if you need more help. Good luck.