Thread: having bad time with basic calculator code

i dont know how to get my test class to work and return a value entered.
my superclass must be abstract while my subclasses have to be concrete(non-abstract)
it seems that i cannot access the addition method from the testclass for some reason

package courseworkz;
public abstract class Coursework{


public void test()
{
if (answer<5000){
return;
}
}

public void view()
{

}

public class addition extends Coursework{


void add(double fnum, double snum)
{

double newanswer = fnum + snum;
newanswer = answer;


}


}

public class subtraction extends Coursework{

public void sub(double fnum, double snum)
{
double newanswer = fnum - snum;
newanswer = answer;

}
}

public class multiplication extends Coursework{

public void multiply(double fnum, double snum)
{
double newanswer = fnum * snum;
newanswer = answer;

}
}

public class division extends Coursework{

public void divide(double fnum, double snum)
{
double newanswer = fnum / snum;
newanswer = answer;

}


}

double fnum; double initial; double snum; double answer;

}

this is my test class


package courseworkz;

public class courseworktest
{
public static void main(String[]args){

addition test = new addition();
test.add(5);

}
}


thanx for the help