Phanso.h

class PhanSo
{
    private:
        int tu;
        int mau;
    public:
        PhanSo(int a=0, int b=1);
        void Rutgon();
        int LayTuSo(){return tu;};
        int LayMauSo(){return mau;};
        void SetTuSo(int value){tu=value;};
        void SetMauSo(int value){mau=value;};
        void Nhap();
        void Xuat();
        PhanSo Cong(PhanSo ps2);
        PhanSo Tru(PhanSo ps2);
};


Phanso.cpp

#include "stdafx.h"
#include "PhanSo.h"
#include "iostream"
using namespace std;
    PhanSo::PhanSo(int a,int b)
    {
        tu=a;
        mau=b;
    }
    void PhanSo::Nhap()
    {
        cout<<"nhap vao tu so";
        cin>>tu;
        cout<<"nhap vao mau so";
        cin>>mau;
    }
    void PhanSo::Xuat()
    {
        cout<<"phan so la:"<<tu<<"/"<<mau<<endl;
    }
    PhanSo PhanSo::Cong(PhanSo ps2)
    {
        PhanSo result;
        result.tu=tu*ps2.mau+mau*ps2.tu;
        result.mau=mau*ps2.mau;
        result.Rutgon();
        return result;
    }
    PhanSo PhanSo::Tru(PhanSo ps2)
    {
        PhanSo result;
        result.tu=tu*ps2.mau-mau*ps2.tu;
        result.mau=mau*ps2.mau;
        result.Rutgon();
        return result;
    }
    int  UCLN(int x,int y)
    {
        while (x!=y)
        {
            if(x>y)
                x=x-y;
            else y=y-x;
        }
        return x;
    }
    void PhanSo::Rutgon()
    {
        PhanSo result;
        int x;
        x=UCLN(tu,mau);
        result.tu=tu/x;
        result.mau=mau/x;
        cout<<"tong sau rut gon la: "<<result.tu<<"/"<<result.mau<<endl;
    }

BT1.cpp

// BT1.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "conio.h"
#include "PhanSo.h"
#include "iostream"
using namespace std;
void main()
{
    PhanSo a,b,c;
    a.Nhap();
    b.Nhap();
    c=a.Cong(b);
    _getch();
}