You define the function to accept 6 arguments as
then you implement the function with 7 arguments as
int change(int&, int&, int&, int&, int&, int&);
pick one and stick with it!
int change (int money, int& hu, int& fi, int& tw, int& tn, int& fiv, int& on)
A function can only return one value, so choose just one to return based on what the function is even doing. If you pass all of the arguments by reference, then you could change it to a "void" function instead of "int", so you dont have to return anything.
return hu, fi, tw, tn, fiv, on ;
This isnt how you call a function. Do something like this instead (of course using your actual variables "hu", "fi", etc)
int change (int hund, int fift, int twent, int ten, int five, int one);
int myResult = change( myArg1, myArg2, etc);