уравнение 5 класса

#include <cstdio>
int main()
{
 int x,xpos;
 char in[5];
 FILE *f=fopen("input.txt","r");
 fscanf(f,"%s",&in);
 fclose(f);
 bool plus=(in[1]=='+');
 if (in[0]=='x') xpos=1;
  else if (in[2]=='x') xpos=2;
   else xpos=3;
 switch (xpos)
 {
  case 1: x=in[4]-'0'-plus*(in[2]-'0')+(!plus)*(in[2]-'0'); break;
  case 2: x=(!plus)*(in[0]-in[4])+plus*(in[4]-in[0]); break;
  case 3: x=in[0]-'0'+plus*(in[2]-'0')-(!plus)*(in[2]-'0'); break;
 }
 f=fopen("output.txt","w");
 fprintf(f,"%d\n",x);
 fclose(f);
 return 0;
}

#include <cstdio>
int main()
{
int sign;
int result;
int a, b, c;
char s[5];
 FILE *f=fopen("input.txt","r");
 fscanf(f,"%s",s);
 fclose(f);
a=s[1]-'0';
b=s[3]-'0';
c=s[5]-'0'
if (s[2]=='+') sign=1;
else sign=-1;
if(s[1]=='x') result=c-(sign)*b;
else
if(s[3]=='x') result=sign*(c-a);
else
if(s[5]=='x') result=a+(sign)*b;
 f=fopen("output.txt","w");
 fprintf(f,"%d",result);
 fclose(f);
 return 0;
}