If we have a conditional that is "If p, then q", the contrapositive is "If not q, then not p".
In this case p is "Toby not eating corn" and q is "he is not hungry". They are already written in negative terms, so the contrapositive will have positive terms for the hypothesis and conclusion.
Then, "not q" is "he is hungry" and "not p" is "Toby is eating corn" ("he" and "Toby" are interchangeable as they refers to the same person).
Then, we write the contrapositive as:
"If Toby is hungry, he is going to eat corn"