I have two programs here I cannot seem to get any return value and I have no idea why, everything I'm doing is just like my book says and I cannot get it working.

The parts commented out are the other ways I was trying to make this work, somethings wrong because they're both not working

This one convert miles to kilometer as many times and increment value you select

int main(int argc, char *argv[])
{
  void conversions(double, int, double);  //prototypes
  double milesToKm(double); 

  double miles = 0;
  int conv = 0;
  double inc = 0;
  
  printf("Enter the miles:\n");
  scanf("%d", &miles);
  printf("Enter the number of times you want to be converted:\n");
  scanf("%d", &conv);
  printf("Enter the increment between conversions:\n");
  scanf("%d", &inc);
  
  conversions(miles, conv, inc);
    
  system("PAUSE");	
  return 0;
}
void conversions( double miles, int conv, double inc)
{
     int i;
     double km;     
     printf("MILES   KILOMETERS\n");
     printf("-----   ----------\n");
     for (i = 0; i < conv; i++){
         km = milesToKm(miles);
         printf("%3.2d    %6.2d\n", miles, km);
//         printf("%3.2d    %6.2d\n", miles, milesToKm(miles));
         miles += inc;
         }
}
double milesToKm(double miles)
{
    double km;
    km = miles * 1.6093;
//    return miles * 1.6093;
    return (km);
}

This one is to calculate win percentage

int main(int argc, char *argv[])
{

  double winPercent(double, double); 
  double win, loss;
  double perWin;
  
  printf("Enter the number of wins:\n");
  scanf("%d", &win);
  printf("Enter the number of losses:\n");
  scanf("%d", &loss);
  
  perWin = winPercent(win, loss);
  
  printf("The win percentage is: \n", perWin);
  
    
  system("PAUSE");	
  return 0;
}
double winPercent(double win, double loss)
{
     double percWin;
     percWin = (100 * win / (win + loss));
     return (percWin);                                     
}

Any help is appreciated, I cannot see anything wrong is my code from what has been taught.

Hello!
About your percentage calculator:

printf("Enter the number of wins:\n");
scanf("%d", &win);
printf("Enter the number of losses:\n");
scanf("%d", &loss);

given that you have defined win and loss as

double

You must use scanf with a different syntax, refer to:
http://www.cplusplus.com/reference/clibrary/cstdio/scanf/
But in short:

scanf("%lf",&win);

is used in the case of doubles.

scanf("%d", &win);

is used when win is an integer.
Moreover...

printf("The win percentage is: \n", perWin);

Here you have messed up the syntax yet again, it should be:

printf("The win percentage is: %lf\n", perWin);

I suggest you read the following:
http://www.cplusplus.com/reference/clibrary/cstdio/printf/
Hope this helps, good luck.

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