Question 344317
You could recognize that 
{{{8=2^3}}} and substitute.
{{{2^n=2^3}}}
{{{n=3}}}
or take the log (base 2) of both sides.
{{{log(2,(2^n))=log(2,(8))}}}
{{{n=log(2,(8))}}}
{{{n=log(10,(8))/log(10,(2))}}}
{{{n=0.90309/0.30103}}}
{{{n=3}}}