Question

(a) translate the argument into symbolic form and (b) determine if the argument is valid or invalid. You may compare the argument to a standard form or use a truth table.

If Nicholas Thompson teaches this course, then I will get a passing grade.

I did not get a passing grade.

∴ Nicholas Thompson did not teach the course.

Answer 1

If a cow, then mammal - hypothesis

If a mammal then a cow - converse, invalid

If not a cow , then not a mammal - inverse, invalid

If not a mammal, then not a cow - contrapositive - true

Here:
If NT teaches, then pass - hypothesis

If pass, then NT - converse, invalid

If not NT, then not pass - inverse, invalid

If not pass, then not NT - contrapositive, true (this is your case)

Answer 2

(a) translate the argument into symbolic form and (b) determine if the argument is valid or invalid. You may compare the argument to a standard form or use a truth table.
If I can get my child to preschool by 9:45AM, then I can take the 9:00AM class.
If I can take the 9AM class, then I can be done by 2PM
If I can get my child to preschool by 8:45AM then I can be done by 2PM