3-7（4）

 #include <iostream>
using namespace std;
class Student
{
public:
	Student(int n,float s):num(n),score(s){}
	//void change(int n,float s)
	void change(int n,float s)const
	{
		num=n;
		score=s;
	}
	//void display()
	void display()const
	{
	 cout<<num<<" "<<score<<endl;
	}
private:
	//int num;
	mutable int num;
	//float score;
	mutable float score;
};
int main()
{
 //Student stud(101,78.5);
 const Student stud(101,78.5);
 stud.display();
 const Student *p = &stud;
 //stud.change(101,80.5);
 p->change(101,80.5);
 //stud.display();
 p->display();
 return 0;
}