1. G⊃(H⊃K)
2. (H∨∼M)⊃∼K
3. H / ∼G ∨ ∼H
4. H∨∼M 3, addition
5. ~K 2,4 modus ponens
6. G⊃(~H∨K) 1, material implication
7. ~G∨(~H∨K) 6. material implication
8. (~G∨~H)∨K 7. association
9. K∨(~G∨~H) 8. commutation
10. ∼G∨∼H 9,5, disjunctive syllogism
Edwin