The property of equality shown in the equation is the Addition Property of Equality. This property states that if two expressions are equal, you can add the same value to both sides of the equation without changing the equality.
In this case, you are adding \(-23\) to both sides of the equation, which maintains the equality:
If \( s - 11 = r \), then \( s - 11 - 23 = r - 23 \).