2.1
#include <iostream>
using namespace std;
int main()
{

const long minutes = 60;
const long hours = 60*minutes;
const long days = 24*hours;

cout << "Введите секунды  : " ;
long seconds;
cin >> seconds;
cout << seconds << " seconds = " ;
if(seconds / days > 0)
    cout << seconds / days << " дней, " ;
seconds %= days ;
if(seconds / hours > 0)
    cout << seconds / hours << " часов, " ;
seconds %= hours ;
if(seconds / minutes > 0)
    cout << seconds / minutes << " минут, " ;
seconds %= minutes ;
cout << seconds << " секунды" ;
return 0;
}
2.2
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

int main()
{
    const double lm1 = 60;
    const double ms1 = 60;

    cout << "Введите широту в градусах, минутах и секундах:" << endl;
    cout << "Во-первых, введите градусы:";
    unsigned short l;
    cin >> l;
    cout << "Далее введите в минутах:";
    unsigned short m;
    cin >> m;
    cout << "Потом введите в секундах:";
    unsigned short s;
    cin >> s;

    float m1, d1, df1;
    m1 = s / ms1;
    d1 = m / lm1;
    df1 = l + d1;

    cout << l << " degrees, " << m << " minutes, " << s << " seconds = " << df1;
    return 0;
}
2.3
#include <iostream>
#include <cmath>
using namespace std;

int main()
{
double a,b,c;
cout <<"Введите численновсть страны а:"<< endl;
cin>>a;
cout <<"Введите численность города b:"<< endl;
cin>>b;
c=(a*100)/b;
cout << c << endl;
    return 0;
}
2.4
#include "iostream"
using namespace std;

 int main()
{
    int nomer = 0;
    cout << "Введите номер: ";
    cin >> nomer;
    int a=0, b=0, c=0, d=0, e=0, f=0;
    a = nomer % 10;
    b = (nomer / 10) % 10;
    c = (nomer / 100) % 10;
    d = (nomer / 1000) % 10;
    e = (nomer / 10000) % 10;
    f = (nomer / 100000) % 10;
    if (a + b + c == e + d + f)
        cout << "Счастливчик" << endl;
    else
        cout << "Неудачник" << endl;
}

2.5
#include <iostream>
#include <cmath>
using namespace std;
int main ()
{
    double x, y, x0, y0, h , v, t;
    const double g=9.8;
    cout <<"Введите h: "<< endl;
    cin>>h;
    cout <<"Введите v:"<< endl;
    cin>>v;
    cout <<"Введите t:"<< endl;
    cin>>t;
    y0=h;
    x0=0;
    x=x0+v*t;
    y=y0+v*t-((g*t*t)/2);
    cout << x << endl;
    cout << y << endl;
 return 0;
}