We can also solve it by the properties.
1.) A <--> ( A v A)
A <--> A (Since A + A is A.)
AA + A'A' ( Since A <--> B is AB +A'B')
Therefore A + A' is 1. Which is a Tautology.
2.) (A v B) --> B
A'B' + B ( Since A-->B is A' + B)
A' + B ( By law of Absorption.)
Hence it is neither Tautology nor Contradiction and Hence Contingency.
3.) A ∧ ( ¬ ( A v B))
Which can be written as
A.(A + B)'
A.(A'B') ( By de-morgan's Law)
A.A'B' = 0.
Hence it is a Contradiction.
-