A.cpp

#include "A.h"
#include <iostream>

using namespace std;

A::A(){
  cout<<"ctor default A"<<endl;
  n = 0;
}
A::A(int nn){
  cout<<"ctor param A"<<endl;
  n = nn;
}
A::A(const A& a){
  cout<<"cctor A"<<endl;
  n = a.n;
}
A::~A(){
  cout<<"dtor A"<<endl;
}
A& A::operator=(const A& a){
  cout <<"opeator = a"<<endl;
  this->n = a.n;
  return *this;
}
A A::operator+(const A& a){
  cout <<"opeator + a"<<endl;
  A A1(this->n+a.n);
  return A1;
}
A A::operator-(const A& a){
  cout <<"opeator - a"<<endl;
  A A1(this->n-a.n);
  return A1;
}
int A::getN(){
  return n;
}

A.h

#ifndef _A_H
#define _A_H

class A {
private:
  int n;
public :
  A();
  A(int nn);
  A(const A& a);
  ~A();
  A& operator=(const A& a);
  A operator+(const A& a);
  A operator-(const A& a);
  virtual int getN();
};
#endif

B.cpp

#include "B.h"
#include <iostream>

using namespace std;

B::B():A(){
  cout<<"ctor default B"<<endl;
  m = 0;
}
B::B(int mm,int nn):A(nn){
  cout<<"ctor param B"<<endl;
  m = mm;
}
B::B(const B& b):A(b){
  cout<<"cctor B"<<endl;
  m = b.m;
}
B::~B(){
  cout<<"dtor B"<<endl;
}
B& B::operator=(const B& b){
  cout <<"opeator = b"<<endl;
  A a = b;
  a.operator=(b);
  this->m = b.m;
  return *this;
}
B B::operator+(const B& b){
  cout <<"opeator + b"<<endl;
  A a = b;
  a.operator+(b);
  B B1(this->m+b.m,b.getN());
  return B1;
}
B B::operator-(const B& b){
  cout <<"opeator - b"<<endl;
  A a = b;
  a.operator-(b);
  B B1(this->m-b.m,b.getN());
  return B1;
}

int B::getN(){
  return A::getN();
}

int main(){
  A A1;
  A A2(5);
  A A3(8);
  A A4 = A2;
  A4 = A2 + A3 - A4;
  return 0;
}

B.h

#ifndef _B_H
#define _B_H
#include "A.h"
class B:public A {
private:
  int m;
public :
  B();
  B(int mm,int nn);
  B(const B& b);
  ~B();
  B& operator=(const B& b);
  B operator+(const B& b);
  B operator-(const B& b);
  int getN();
};
#endif

ini :

B B::operator+(const B& b){
cout <<"opeator + b"<<endl;
//A a = b;
A::operator+(b);
B B1(this->m+b.m,A::n);
return B1;
}

Jalan, syaratnya member kelas A harus bukan private