Python:

while True:
	try:
		a,b,c=map(int,input().strip().split())
		print(f"{a+b+c:.2f} {(a+b+c)/3:.2f}")
	except:
		break

参考答案：

#include<iostream>

using namespace std;

int main()
{
    double a, b, c;
    cin >> a >> b >> c;

    printf("%.2lf ", a + b + c);
    printf("%.2lf ", (a + b + c) / 3);

    return 0;
}