#include <iostream>
#include <string>

using namespace std;

int main() {
    int n, number;
    cin >> n;

    double totalGrades = 0;
    double totalCredits = 0;

    for (int i = 0; i < n; i++) {
        cin >> number;
        int grade = number % 10;
        double credit = (int)number / 10;

        totalGrades += grade;

        if (grade == 2) {
            credit = 0;
        }
        else if (grade == 3) {
            credit *= 0.50;
        }
        else if (grade == 4) {
            credit *= 0.70;
        }
        else if (grade == 5) {
            credit *= 0.85;
        }

        totalCredits += credit;
    }

    printf("%.2f\n%.2f\n", totalCredits, totalGrades / n);

    return 0;
}
    
Решение с тернарен оператор:

#include <iostream>
#include <string>

using namespace std;

int main() {
    int n, number;
    cin >> n;

    double totalGrades = 0;
    double totalCredits = 0;

    for (int i = 0; i < n; i++) {
        cin >> number;
        int grade = number % 10;
        double credit = (int)number / 10;

        totalGrades += grade;

        credit *=
            grade == 2 ? 0 :
            grade == 3 ? 0.50 :
            grade == 4 ? 0.75 :
            grade == 5 ? 0.85 : 1;

        totalCredits += credit;
    }

    printf("%.2f\n%.2f\n", totalCredits, totalGrades / n);

    return 0;
}