I use slightly different symbols than you, but you can figure them out: 1. K->L 2. ~KvF 3. (L&F)->A 4. ~A // ~K 5. ~A->~(L&F) 3, contrapositive 6. ~(L&F) 5,4 hypothetical syllogism 7. ~Lv~F 6, deMorgan's 8. ~L->~K 1, contrapositive 9. K->F 2, writing a disjunction as a conditional 10. ~F->~K 9, contrapositive 11. ~Kv~K 8,10,7, constructive delimma 12. ~K 11, idempotent law Edwin