四则运算

#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;
}