C :

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
  int x,y,z;
  for(x=0;x<=20;x++)
  for(y=0;y<=33;y++)
  {
     if(100-x-y==300-15*x-9*y)
     printf("%d %d %d\n",x,y,100-x-y);
  }

  return 0;
}

C++ :

#include<iostream>
using namespace std;
int main()
{
  float a,b,c;
  for (a=0;a<=20;++a)
  for (b=0;b<=34;++b)
  for (c=0;c<=100;++c)
  if ((5*a+3*b+c/3==100)&&(a+b+c==100))
  { cout<<a<<" "<<b<<" "<<c;
    cout<<endl;}
   return 0;
}