Help me in solving AVG problem

help
,
1

My issue

i cant understand this problem statement

My code

# cook your dish here

Problem Link: Average Number Practice Coding Problem

2

@nageswarijampa
here plzz refer the following solution for better understanding

#include <iostream>
using namespace std;

int main() {
	// your code goes here
	int t;
	cin>>t;
	while(t--)
	{
	    int n,k,v;
	    cin>>n>>k>>v;
	    int a[n];
	    int sm=0;
	    for(int i=0;i<n;i++)
	    {
	        cin>>a[i];
	        sm+=a[i];
	    }
	    v=v*(n+k);
	    v-=sm;
	    if(v%k==0&&v>0)
	    cout<<v/k;
	    else
	    cout<<-1;
	    cout<<endl;
	}
	return 0;
}