5

1. –(∃x)Hx

Premise

2. –[–(x)Hx]

Premise

3. (x)–Hx

From 1 by Q.E.

4. –Ha

From 3 by U.I.

5. (x)Hx

From 2 by Double negation.

6. Ha

From 5 by U.I.

7. Ha&–Ha

From 6, 4 by adjunction

1. (x)Gx

Premise

2. (∃x)–Gx

Premise

3. –Ga

From 2 by E.I.

4. Ga

From 1 by U.I.

5. Ga&–Ga

From 4, 3 by adjunction