Answer
See below.
Work Step by Step
The sentence in "if...then" form is: If a person diets, then he or she loses weight.
The contrapositive of $p\rightarrow q$ is $\sim q\rightarrow p$.
The converse of $p\rightarrow q$ is $q \rightarrow p$.
The inverse of $p\rightarrow q$ is $\sim p\rightarrow q$.
Hence here the converse is: If a person loses weight, then he or she is dieting. The inverse: If a person is not dieting, then he or she is not losing weight. The contrapositive: If a person is not losing weight, then he or she is not dieting.
