我一开始不知道权重是什么，后来弄明白了，但提交不对。后来我找到两处错误：第1我输出的时候没加点，第2输出的时候冒号没加空格。

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
    //freopen("xxx.in","r",stdin);
    //freopen("yyy.out","w",stdout);
    double N1,N2,N3,N4,Y;
    cin >> N1 >> N2 >> N3 >> N4;
    double X;
    X=N1*2/10+N2*3/10+N3*4/10+N4*1/10;
    cout << "Media: " << fixed << setprecision(1) << X << endl;
    if(X>=7.0)
        cout << "Aluno aprovado." << endl;
    else if(X<5.0)
        cout << "Aluno reprovado." << endl;
    else if(X>=5.0 && X<7.0)
    {
        cout << "Aluno em exame." << endl;
        cin >> Y;
        cout << "Nota do exame: " << Y << endl;
        double Z;
        Z=(X+Y)/2;
        if(Z>=5.0)
            cout << "Aluno aprovado." << endl;
        else
            cout << "Aluno reprovado." << endl;
        cout << "Media final: " << fixed << setprecision(1) << Z << endl;
    }
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}