To raise \( n \) to the 8th power, you calculate \( n^8 \). Then, to find the difference between \( n^8 \) and 7, you subtract 7 from the result:
\[ n^8 - 7 \]
So, the final expression is \( n^8 - 7 \). If you have a specific value for \( n \), you can substitute it into the expression to get a numerical result.