Here is a proof using the Introduction and Elimination Rules of Natural Deduction: 1. M ⊃ (∼B ⊃ J) 2. B ⊃ (~M * ~M) 3. ∼J / ∴ ~M ---------------------------------------- 4. M Assumption 5. ~B ⊃ J 1,4 ⊃E 6. B Assumption 7. ~M & ~M 2,6 &I 8. ~M 7 &E 9. M & ~M 4,8 &I 10. ~B 6-9 ~I 11. B & ~B 6,10 &I 12. ~M 4-11 ~I QED HERE is a Proof using Copi Rules: 1. M ⊃ (∼B ⊃ J) 2. B ⊃ (~M * ~M) 3. ∼J / ∴ ~M ---------------------------------------- 4. B ⊃ (~M & ~M) 2 Tautology 5. ~(~B ⊃ J) ⊃ ~M 4 Transposition 6. (~B ⊃ J) v ~M 5 Material Implication 7. ~ ~B v J v ~M 6 Material Implication 8. B v J v ~M 7 Double Negation 9. (B v ~M) v J 8 Association 10. B v ~M 9 Disjunctive Syllogism 11. ~B ⊃ ~M 10 Material Implication 12. M ⊃ B 11 Transposition 13. M ⊃ ~M 4,12 Hypothetical Syllogism 14. ~M v ~M 13 Material Implication 15. ~M 14 Tautology QED