sum using for loop in c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>


/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char *argv[]) {
	int x,i,n,num, f = 1;
    double k=3,e=2.71828;
    printf("Enter a number to calculate its factorial: ");
    scanf("%d", &x);
    for (x = 1; x <= n; x++){
    f = f *x;
    }  
    printf("enter number to calculate its probability: ");
    scanf("%d",&num);
    if (num=x,num<=10){
		for (i=1;i<=num;i++){
	 double p=((pow(k,x))*(pow(e,-k)))/f;
	 printf("The probability is %f\n",p);}
	}
	else {
		printf("this number is not between 1 to 10");
	}