Question 1032740
~A -> H
H -> D
~D
--------
∴ A

1. ~A -> H -------Hypothesis
2. H -> D -------Hypothesis
3. ~A -> D -------Hypothetical syllogism on #1 and #2
4. ~D -> ~~A -----Contrapositive of #3
5. ~D -> A  ------double negation
6. ~D   ----------Hypothesis
7. A   -----------modus ponens on #5 and #6.