if i do 2^(7+1) = 256, how can i perform something on 256 to = 7?

Who do you want the ok from ?      

Thanks from me, I am not use if that is what you really want.  

Are you looking for a thank you of the poster?   (We all like those but they are often not forthcoming.)

or

do you want a mathematician to confirm your answer?

$$\\2^{(7+1)} = 256\\
log_22^{(7+1)} = log_2256\\
(7+1)*log_22 = log_2256\\
7+1 = log_2256\\
7 = (log_2256)-1\\
so\\
(log_2256)-1=7$$

$${{log}}_{{\mathtt{2}}}{\left({\mathtt{256}}\right)}{\mathtt{\,-\,}}{\mathtt{1}} = {\mathtt{7}}$$

$${{log}}_{{\mathtt{2}}}{\left({\mathtt{256}}\right)}{\mathtt{\,-\,}}{\mathtt{1}} = {\mathtt{7}}$$

😻 I already posted the answer twice. 😻 

$${{log}}_{{\mathtt{2}}}{\left({\mathtt{256}}\right)}{\mathtt{\,-\,}}{\mathtt{1}} = {\mathtt{7}}$$  

okay