Deny the Antecedent – Invalid (always)

P1 If you bring tea to class, you’ll be happy.

P2 You do not bring tea to class

C You aren’t happy.

Modus Tollens – (Valid)

P1 If you bring tea to class you’ll be happy

P2 You’re not happy

C You did not bring to class

Hypothetical Syllogism – (valid)

P1 If you bring tea to class, than you’ll be warm

P2 <if you’re warm>, then you’ll be happy

C If you bring tea to class you’ll be happy

Affirm the consequent – (invalid)

P1 If you bring tea to class you’ll be warm

P2 You’ll be warm

C You bring tea to class

Disjunctive syllogism – (valid)

P1 you’ll bring tea OR coffee

P2 You don’t bring tea

C You brought coffee