1. PvR Premise

2. ~Pv(Q.R) Premise

3. R→Q.S Premise
…………..

Q.S

Proof

4. (~PvQ).(~PvR) 2 DMorgan

5. ~PvR 4. Simplification

6. (P. ~P)vR 1,5 Conjunction

7. R 6 Simplification

8. Q.S 3,7 Modus Ponen

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