Error 'sscanf_result' undeclared (first use in this function) - c

Question

Well that's my code and i get this errors
In function 'main':
41 1 [Error] 'scanf_result' undeclared (first use in this function)
41 1 [Note] each undeclared identifier is reported only once for each function it appears in
#include <stdio.h>
#include <stdlib.h>
int main ( int argc, char *argv[] )
{
int n;
float fl,fw,wh,ww,dh,dw;
float p,t;
float tl,tw,a;
float p1,p2,p3;
printf("What's the width of the floor?");
scanf ("%d", &fw);
printf("What's the length of the floor?");
scanf ("%d", &fl);
printf("What's the height of the wall?");
scanf ("%d", &wh);
printf("What's the width of the wall?");
scanf ("%d", &ww);
printf("What's the width of the door?");
scanf ("%d", &dw);
printf("What's the height of the door?");
scanf ("%d", &dh);
a=fw*fl+(wh*ww)*3-(dh*dw);
p1=a*22;
p2=a*23.80;
p3=a*14;
char line[100];
int answer;
answer = -1;
while (answer != 0)
{
printf ("\nWhat tiles do you want?:\n");
printf (" [1] 20sm X 30sm.");
printf (" [2] 30sm X 41,6sm");
printf (" [3] 25sm X 33sm");
printf ("\nWhat do you want to do? [0 for nothing] ");
fgets (line, sizeof(line), stdin);
scanf_result = scanf (line, "%d", &answer);
if ((scanf_result == 0) | (scanf_result == EOF))
{
printf ("\n *** 1 - 2 or 3! ***\n");
answer = -1;
}
switch (answer)
{
case 0:
break;
case 1:
printf(" Total price = %.2f lv \n",p1);
break;
case 2:
printf(" Total price = %.2f lv \n",p2);
break;
case 3:
printf(" Total price = %.2f lv \n",p3);
break;
default:
break;
}
}
system("PAUSE");
return 0;
}

Answer 1

As the error message clearly describes it, there is no declaration for scanf_result variable in your program.
Put a:
int scanf_result;
in your declaration section to fix the error.

Answer 2

scanf_result = scanf (line, "%d", &answer);
Your scanf() usage is wrong. you need sscanf() instead.
The scanf() function shall read from the standard input stream stdin. The sscanf() function shall read from the string line.
[Error] 'scanf_result' undeclared (first use in this function)
Error describes what you are missing.
declare scanf_result
sscanf() returns integer
declare as integer variable.