Нет совпадения для оператора = (типы операндов - это std :: basic_ostream и int)
result_1 += number_1;
cout << result_1;
Excited Elk
result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;result_1 += number_1;
cout << result_1;