unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    txtA: TEdit;
    txtB: TEdit;
    txtC: TEdit;
    txtR: TEdit;
    Button1: TButton;
    Button2: TButton;
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button2Click(Sender: TObject);
begin
 close;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
 A,B,C,R   : integer;
begin
 A:=StrToInt(txtA.Text);
 B:=StrToInt(txtB.Text);
 C:=StrToInt(txtC.Text);

 R:=a+b+c

 txtR.Text:=IntToStr(r)
end;

end.