1. A->(QvR) 2. (R&Q)->B 3. A&~B Conclusion: R<->~Q 4. ~B 3,simp. 5. ~B->~(R&Q) 2,CP 6. ~(R&Q) 5,4,MP 7. ~Rv~Q 6,DM 8. ~~R->~Q 7,writing a disjunction as a conditional 9. R->~Q 8,DN 10. A 3,simp 11. QvR 1,10,MP 12. ~~QvR 11,DN 13. ~Q->R 10,writing a disjunction as a conditional 14. (R->~Q)&(~Q->R) 9,13,conjunction 15. R<->~Q 14, definition of biconditional Edwin