Why don't you test it to see if it works? Once you test it, you will see that in line 15, you are attempting to pass variables that don't exist in the main() function (namely the variables called a, c, and d).
I think your function far() should be simplified to accept a single parameter. Something like this:
1 2 3 4 5
double far(double c)
double f = etc; // do the calculation here;
In the existing code, the lines are in the wrong order: a=9,c=5,d=32; these values are assigned too late, after they have already been used. But really, you don't need individual variables, just put the numbers direct into the calculation. Be careful to use 9.0 and 5.0 so that floating-point rather than integer division will be done.