I'm getting the error message "Error: expected initializer before 'sum' " from line 9 of my code when I try to compile my program. I can't seem to figure out why it would be throwing this error. Any help would be great. Thanks!

```
#include <iostream>
using namespace std;
struct Frac;
{
int numerator;
int denominator;
}
Frac sum(Frac& fract1, const Frac& fract2);
Frac Sub(Frac& fract1, const Frac& fract2);
Frac Mul(Frac& fract1, const Frac& fract2);
Frac Div(Frac& fract1, const Frac& fract2);
```