C++ Error: 'center' was not declared in this scope

This error message indicates that the variable 'center' has not been declared within the current scope. This means it has not been defined or initialized before being used. The code attempts to assign a value to 'center' using a mathematical expression involving the x-coordinates of two points. However, since 'center' is undefined, the compiler cannot recognize it. To fix this error, you need to declare and initialize 'center' before using it in this expression.