I have got to use functions to do the calculations...my problem is I am trying to send solve back to the main ()...I've worked on this for all day...here is the source code:

//PROBLEM: math choice

#include <iostream.h>

#include <conio.h>

#include <iomanip.h>

void multiply();

void divided();

void adding();

void subtract();

int main(){

float a,b,solve;

char sign, answer;

do{

cout<<"Please enter your mathematical"<<endl;

cout<<"expression: ";

cin>>a;

cin>>sign;

cin>>b;

switch (sign){

case '+': { adding();

break;}

case '-': { subtract();

break;}

case '*': { multiply();

break;}

case '/': { divided();

break;}

default : {cout<<"Please choose either +,-,*, or /."<<endl;}}

if((sign=='+')||(sign=='-')||(sign=='*')||(sign=='/')){

cout<<"Your expression, "<<a<<sign<<b<<" = "<<solve<<endl;}

cout<<"Would you like to enter another expression?"<<endl;

cout<<"Enter 'y' for yes and 'n' for no. Answer: ";

cin>>answer;

}while(answer=='y');

getch();

return 0;}

//math evaluation functions

void adding(a,b,solve){

solve=a+b;}

void subtract(a,b, solve){

solve=a-b;}

void multiply(a,b,solve){

solve=a*b;}

void divided(a,b,solve){

solve=a/b;}

////// Here are my errors:

[Linker Error] Unresolved external 'adding()' referenced from D:\PROGRAM FILES\BORLAND\CBUILDER4\PROJECTS\MATHCHOICE.OBJ.

[Linker Error] Unresolved external 'subtract()' referenced from D:\PROGRAM FILES\BORLAND\CBUILDER4\PROJECTS\MATHCHOICE.OBJ.

[Linker Error] Unresolved external 'multiply()' referenced from D:\PROGRAM FILES\BORLAND\CBUILDER4\PROJECTS\MATHCHOICE.OBJ.

[Linker Error] Unresolved external 'divided()' referenced from D:\PROGRAM FILES\BORLAND\CBUILDER4\PROJECTS\MATHCHOICE.OBJ.

/////SOMEBODY PLEASE HELP ME!!!!