1. A→B
2. A→~(C∨B) ∴ ~A
3. A→(~C&~B) 2, DeMorgan's theorem
4. A→~B 3, Decomposition (simplification) of a conjunction
5. ~B→~A 1, Modus Tollens
6. ~~B→~A 4, Modus Tollens
7. B→~A 7, Double negation
8. B∨~B Tautology (law of excluded middle)
9. ~A 7,5,8, disjunctive elimination (disjunctive syllogism)
1. (A&~B)&(~C∨D)
2. ~[(D&A)&~B] ∴ ~C
3. ~[D&(A&~B)] 2,Association
4. ~D∨~(A&~B) 3,DeMorgan's theorem
5. A&~B 1,Decomposition (simplification) of a conjunction
6. ~D 4,5, disjunctive elimination (disjunctive syllogism)
7. ~C∨D 1,Decomposition (simplification) of a conjunction
8. ~C 7,6, disjunctive elimination (disjunctive syllogism)
Edwin