Well, the commands worked, but not as expected.
You will have to open the group file in an editor and remove the redundant flyerdan69. You will have to use the sudo command with the editor. Probably gedit is installed
sudo gedit /etc/group
the lines to be altered:
The lp group doesn't exist, probably it isn't needed.
Note that you will have to logout and afterwards login after changing the group file in order the changes to take place.