(i) Truth table for ¬ (p ∧ q)
Truth table for ¬ p ∨ ¬ q
The entries in the column ¬ (p ∧ q) and ¬ p ∨ ¬ q are identical. So, ¬ (p ∧ q) ≡ ¬ p ∨ ¬ q
(ii) Truth table for ¬ (p → q)
The entries in the column ¬ (p → q) and p ∧ ¬ q are identical and hence they are equivalent.