Invalid or valid

Question

All nonengineers are not mathematicians. Bobby is a mathmetician. Therefore, Bobby is an engineer.

Answer 1

~e → ~m          if true, the contrapositive is true

m → e               

b → m               by Law of Syllogism

b → e

Answer 2

By the first statement, if a person is not an engineer, then that person is not a mathematician.  Since Bobby is a mathematician, he must be an engineer. 

 

The given statement is valid.