1. ~ (A v B)
2. E -> B
3. E v (G -> U)
4. H v (W & X)
5. (H v X) -> (U -> O) / G -> O
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6. (H v W) & (H v X) 4 Distribution
7. (H v X) & (H v W) 6 Commutation
8. H v X 7 Simplification
9. U -> O 5,8 Modus Ponens
10. ~A & ~B 1 De Morgan's Law
11. ~B & ~A 10 Commutation
12. ~B 11 Simplification
13. ~E 2,12 Modus Tollens
14. G -> U 3,13 Disjunctive Syllogism
15. G -> O 14,9 Hypothetical Syllogism