Short of handing your homework to you on a plate (it's not likely to happen), this is as far as I can go showing you the way.

Code:

#include <iostream>
#include <cmath>
using namespace std;
int main() {
double x = 0.8;
double sum = 0.0;
for ( int n = 0 ; n <= 10 ; n++ ) {
double pow_term = pow(x,n);
// double fact_term = .....
cout << "n=" << n << " pow(x,n)= " << pow_term << endl;
sum = sum + pow_term /* / fact_term */;
}
cout << "Sum = " << sum << endl;
return 0;
}

All you need do is uncomment the fact_term bits and work out how to calculate factorial(n)