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