maximum so zloženou podmienkou

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Button1: TButton;
    Label4: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
a,b,c:integer;
begin
a:=StrToInt(Edit1.Text);
b:=StrToInt(Edit2.Text);
c:=StrToInt(Edit3.Text);

if (a>b) And (a>c) then
    begin
      label4.caption:=inttostr(a);
    end else
            begin
              if (b>a) And (b>c) then
                    begin
                      label4.caption:=inttostr(b);
                    end else
                            begin
                              label4.caption:=inttostr(c);
                            end;
    end;

end;

end.