Answer quastion 1

#include<iostream>
using namespace std;
int main()
{
    int b[3][3],i,j,sum1=0,sum2=0,sum=0;
    for(i=0;i<3;i++)
    {
        for(j=0;j<3;j++)
        {
            cout<<"["<<i<<"]["<<j<<"]";
            cin>>b[i][j];
        }
    }
    for(i=0;i<3;i++)
    {
        for(j=0;j<3;j++)
        {
            cout<<b[i][j]<<"\t";
        }
        cout<<endl<<endl;
    }

    for(j=0;j<3;j++)
    {
        sum1+=b[2][j];
    }
    for(i=0;i<3;i++)
    {
        sum2+=b[i][0];
    }
    sum=sum1+sum2;
    float av=sum/3;
    cout<<endl<<"av = "<<av<<endl;
}