Determine if the argument is valid and justify.
1) Students must show up to the final or they will receive a grade deduction.
2) Charlie didn’t receive the grade deduction.
∴ Charlie showed up to the final.
Invalid because the argument assumes all numbers divisible by 3 are divisible by 6
Valid because it takes the form of disjunctive syllogism
Invalid because the conclusion does not follow from the premises
Valid because it uses contrapositive reasoning (modus tollens).