subtracting fractions in classes

Hi

I am having difficulty in creating a function for subtracting fractions in a class. I was given this advice to do it

Quote:

Note:subtraction can be achieved by adding (by changing the sign of the numerator - this can be achieved by multiplying it by -1).

and my attempt is shown below:

Code:

`void Fraction::subtract(Fraction f2, Fraction& f3)`

{

int s_denom = denom * f2.denom ;

int s_num = ((num * -1) * f2.denom) - ((f2.num * -1) * denom);

f3.create(s_num,s_denom);

f3.simplify();

}

but a subtraction seems to come out a little wrong for example the output is:

Code:

`Enter first numerator: 3`

Enter first denominator: 4

Enter second numerator: 2

Enter second denominator: 4

3/4 - 2/4 = -1/4

Can anyone help me to correct this little error.

Thanks if you can.