Ok, I downloaded your .cpp file from your other post on the same topic.
A couple pointers that I have for your program:
1) Use set width, this will eliminate readbility issues when others look at your code. [i.e. setw ( 13 )]
2) A lot of times you can initialize variables that are a group of things, then call it in the function later. Again mostly readability and will eliminate a lot of double coding.
double numgroups20 = (a + b + c) / 20; // initialize first
cout << "The number of groups of 20 are: " << numgroups20 << endl; // imagine how much easier it is to code this way
calling out this statement four times in the function
3) Not too sure why you have a cin command at the end of your entire program. I could see something like this being used if you have a loop function, but you don't so I took it out.
cout << "The number of groups of 20 are: " << ((a + b + c) / 20 )<< endl;
Well, take a look at the code and test every possible solution. If this works for you, then great. I know I didn't change a lot of things. And I know I stated above the things I would change, but some of those are general pointers that will help you in future code. If you would like help in changing your current code to make the program more readable then I will be glad to help.