Trouble with exercise

I believe that I am doing the exercise right when I put in

#include <iostream>
#include <cmath>

// Add declarations here:
double average(double num1, double num2);
int thenth_power(int num);
bool is_palindrome(std::string text);

double average(double num1, double num2) {
  return (num1 + num2) / 2;
}

int tenth_power(int num) {
  return pow(num, 10);
}

bool is_palindrome(std::string text) {
  std::string reversed_text = "";
  
  for (int i = text.size() - 1; i >= 0; i--) {
    reversed_text += text[i];
  }
  
  if (reversed_text == text) {
    return true;
  }
  
  return false;
}

int main() {
  
  std::cout << is_palindrome("racecar") << "\n";
  std::cout << tenth_power(3) << "\n";
  std::cout << average(8.0, 19.0) << "\n";
  
}

but it says that the answer is wrong. The hints and solutions are no help. The exercise is https://www.codecademy.com/courses/learn-c-plus-plus/lessons/cpp-functions-scope-flexiblity/exercises/cpp-functions-multifile-programs?action=resume_content_item

Check out the comment to your code. Hope this helps && happy coding!