Random equation

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void rating(int score,int counter);
int main ()
{
  srand (time (NULL));
  int ans;
  int a,b;
  int c, d;
  int score = 0;
  int counter = 0;
  char ch;
  
  puts ("press 'm' for minigame or 'f' for full game\n");
  scanf ("%c", &ch);

  switch (ch)
    {
//questions

    case 'M':
    case 'm':
      {
	printf ("\nwhat is %5d\n\t%5d  +\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	c = a + b;
	counter = counter + 1;
	if (ans == c)
	  {
	    printf ("\ngood!");
	    score = score + 1;
	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", c);
	  }
//1 +

	printf ("\nwhat is %5d\n\t%5d  -\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	d = a - b;
	counter = counter + 1;
	if (ans == d)
	  {
	    printf ("\ngood!");
	    score = score + 1;
	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", d);
	  }
//2 -

	printf ("\nwhat is %5d\n\t%5d  +\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	c = a + b;
	counter = counter + 1;
	if (ans == c)
	  {
	    c = a + b;
	    score = score + 1;

	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", c);
	  }		
// 3 +  	  
      }				//end case'm'
      break;
//end minigame


    case '\n':
    case '\t':
    case ' ':
      break;

    case 'f':
    case 'F':
      {
	printf ("\nwhat is %5d\n\t%5d  +\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	c = a + b;
	counter = counter + 1;
	if (ans == c)
	  {
	    printf ("\ngood!");
	    score = score + 1;
	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", c);
	  }
//1 +

	printf ("\nwhat is %5d\n\t%5d  -\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	d = a - b;
	counter = counter + 1;
	if (ans == d)
	  {
	    printf ("\ngood!");
	    score = score + 1;
	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", d);
	  }
//2 -

	printf ("\nwhat is %5d\n\t%5d  +\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	c = a + b;
	counter = counter + 1;
	if (ans == c)
	  {
	    printf ("\ngood!");
	    score = score + 1;

	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", c);
	  }
//3 +
	printf ("\nwhat is %5d\n\t%5d  -\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	d = a - b;
	counter = counter + 1;
	if (ans == d)
	  {
	    printf ("\ngood!");
	    score = score + 1;

	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", d);
	  }
//4 -

	printf ("\nwhat is %5d\n\t%5d  +\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	c = a + b;
	counter = counter + 1;
	if (ans == c)
	  {
	    printf ("\ngood!");
	    score = score + 1;
	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", c);
	  }
//5 +

	printf ("\nwhat is %5d\n\t%5d  -\n          ---\t\n", a =
		1 + (rand () % 250), b = 1 + (rand () % 250));
	scanf ("%d", &ans);
	d = a - b;
	counter = counter + 1;
	if (ans == d)
	  {
	    printf ("\ngood!");
	    score = score + 1;
	  }
	else
	  {
	    printf ("\nwrong");
	    printf ("\tit's %d\n", d);
	  }
//6 -
      }				//end case'f'
      break;

    }				//end switch//end queostions.

rating(score, counter);//rating


}				//end main

void rating(int score,int counter){
//full game rating
  if (counter == 6)
    {

      if (score == counter)
	{
	  printf ("\nbravo! full mark\n %d out of %d", score, counter);
	}

      if (score == 5 || score == 4)
	{
	  printf ("\nNice marks!\n %d out of %d", score, counter);
	}

      if (score == 3)
	{
	  printf ("\nneeded more practice\n %d out of %d", score, counter);
	}

      if (score == 1 || score == 2)
	{
	  printf ("\nthat's bad 0o0\n %d out of %d", score, counter);
	}
      if (score == 1)
	{
	  printf ("\nbut at least you'v solved one :p\n ");
	}

      if (score == 0)
	{
	  printf ("\nHave you ever got to a school once :/\n %d out of %d",
		  score, counter);
	}
    }				//end full game rating


//minigame rating
  if (counter == 3)
    {

      if (score == counter)
	{
	  printf ("\nbravo! full mark :D\n %d out of %d", score, counter);
	}

      if (score == 2)
	{
	  printf ("\nnot bad ;)\n %d out of %d", score, counter);
	}

      if (score == 1)
	{
	  printf ("\nneeded more practice :p\n %d out of %d", score, counter);
	}

      if (score == 0)
	{
	  printf ("\n needed a ton of practice-_- \n %d out of %d", score,
		  counter);
	}
    }				//end minigame rating
//end rating
}