Propostional logic help?

11. (P & R) → S, S ↔ T, ─T ├ R → ─P 12. P v Q, P → (T → S), P → T, S ↔ Q ├ S 13. A→(B→C), B & &

11. (P & R) → S, S ↔ T, ─T ├ R → ─P

12. P v Q, P → (T → S), P → T, S ↔ Q ├ S

13. A→(B→C), B & −C ├ −A

14. R & S, S → (P → Q), Q → P ├ P ↔ Q

or:11. (P & R) \u2192 S, S \u2194 T, \u2500T \u251c R \u2192 \u2500P 12. P v Q, P \u2192 (T \u2192 S), P \u2192 T, S \u2194 Q \u251c S 13. A\u2192(B\u2192C), B & \u2212C \u251c \u2212A 14. R & S, S \u2192 (P \u2192 Q), Q \u2192 P \u251c P \u2194 Q

or:Now I only need problems 11 and 12

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