Panel 1: We lead off with a grim Elly angrily scraping old gum off Mike's bedposts as he explains that he's been saving it. Given the amount of gum, I'd say that he's being doing it for some time and she just now noticed.
Panel 2: She then lays down the law. No more gum for him. No flexibility from her because he did something she never anticipated.
Panel 3: He then yells "But MA!!" in big red letters as if it would get her to be lenient.
Panel 4: Fortunately for him, she's not smart enough to have found his stash on the dresser. Or, for that matter, look for it in the first place.
Summary: Elly never did learn from her mistakes, did she? She's the sort of person who, if she sees something she does isn't working, does more of the same failed thing.