四则运算升级

源程序：

#include <stdlib.h>
#include<stdio.h>
#include <iostream.h>
#include <conio.h>
#include <time.h>
int main()
{
  int a = 0;
  int b = 0;
  int mode = 0;
  int c=0;
  int result = 0;
  int score = 0;
  int i = 0;
  int n;
  int x;
  for(i=0;i<30;i++)
  {
     a = rand() % 100;
     b = rand() % 100; 
     mode = rand() % 4;     
     printf("%d", a);  
     switch(mode)       
  {         
         case 0:
    printf("+ ");              
             result= a + b;        
          break;         
         case 1:
    printf("- ");              
             result= a - b;              
          break;
   case 2:
    printf("x ");              
             result= a * b;             
          break;         
         case 3:              
             printf("÷ ");              
             result= a / b;
          break;         
          default:             
             printf("somethingis wrong!\n");              
          break;        
  }
     printf("%d = ", b);
     if(result==a/b&&a!=4&&b!=2)
  {
   scanf("%d/%d",&n,&x);
      getchar();
      if(n/x==a/b)
   {
    score+= 10;           
             printf("Right\n\n");
   }
         else      
   {
             printf("Wrong\n\n");
             getchar();      
   }
  }
    else
 {
  scanf("%d",&c);
        getchar();
        if(c==result)        
  {
   score+= 10;           
            printf("Right\n\n");
  }
  else      
  {
   printf("Wrong\n\n");
            getchar();
  }
 }
 }
   printf("Yourscore is: %d\n\n\n", score);  
   return 1;
}

输很长字母，还是会出错，不知道怎么解决！