Answer 1

class person
{int age;
public void person()
age+=5;
}

Answer 2

class Person
{
int age;
public:
int ageIncrement (int age)
{
age += 5;
return age;
}
}

int main ()
{
Person p1;
cout << "Enter age to increment" << endl;
cin >> p1.age >> endl;
cout << ageIncrement(p1.age) << endl;
getchar ();
return 0;
}