procedure TForm1.edt15Exit(Sender: TObject);
var
a,b,c:Double;
begin
if not TryStrToFloat(Trim(edt14.Text),a) then
begin
ShowMessage('请输入数字');
edt14.SetFocus;
exit;
end;
if not TryStrToFloat(Trim(edt15.Text),b) then
begin
ShowMessage('请输入数字');
edt15.SetFocus;
exit;
end;
c:=b/(a+b)*100;
edt22.Text:=FloatToStr(round(c))+'%' ;