You really need to go back and look at your book on the structure of a C++ program. You started to make a function, but left out the function header.
#include <iostream>
using namespace std;
int main()
{
int pradinis = 7;
int tarpinis = pradinis + pradinis % 50;
int galutinis = tarpinis / (tarpinis + 30);
cout << galutinis<< endl;
return 0;
}