can someone give me a hint on how I can fix this function:

void computeOrder(int& spoolOrderAmount, int& spoolStockAmount, double shippingHandling = 10.00)

the third parameter is supposed to be a default argument.

this is the error:

default argument given for parameter 3 of 'void computeOrder(int&, int&, double)' [-fpermissive]

How did you declare your function?

The function/prototype should be defined as:

void computeOrder(int& spoolOrderAmount, int& spoolStockAmount, double shippingHandling = 10.00);

and the implementation as:

void computeOrder(int& spoolOrderAmount, int& spoolStockAmount, double shippingHandling)
{
    // code
}