1. O --> (H * M) 2. (O --> G) --> (H --> ~M) 3. ~G --> (~H v ~M) .·. H --> ~M 4. ~(~H v ~M) --> ~~G 3, Transposition 5. (~~H * ~~M) --> ~~G 4, DeMorgan's Law 6. (H * M) --> G 5, Double Negation 7. O --> G 1,6, Hypothetical Syllogism 8. H --> ~M 2,7, Modus Ponens Edwin