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Pardon Me?
DOT Division 2.2 is for nonflammable compressed gases.
Three years ago, Dot was twelve and her cousin was six. Therefore, Dot is 15 and her cousin is nine. Hence 9+15=24. :)
DOT Division 4.2 is for non-flammable compressed gases.
A dot diagram (also called an Electron Dot Diagram, and a Lewis Structure) is a way to show the valence electrons that surround an element.
See related link for a good lesson on how to make a dot diagram.