Question 954603
<pre>
{{{7^(n+3)=80}}}

Take logs of both sides

{{{log((7^(n+3)))=log((80))}}}

{{{(n+3)log((7))=log((80))}}}

Divide both sides by log(7):

{{{n+3=log((80))/log((7))}}}

Subtract 3 from both sides:

{{{n=log((80))/log((7))-3}}}

Get a calculator:

{{{n=-0.7480837762}}}

Note: you can use "ln" (natural logarithm) instead of 
"log" (common logarithm) and get the same answer.

Edwin</pre>