To rewrite the equation in terms of \( s \), we start with the equation \( s + p = 20 \) and subtract \( p \) from both sides:
\[ s + p - p = 20 - p \]
This simplifies to:
\[ s = 20 - p \]
Now we have rewritten the equation in terms of \( s \):
\[ s = 20 - p \]