Answer: If my mom does not have to work, then I do not babysit my little sister.
Explanation:
The contrapositive of a statement of the form " If a then b" is given by :-
"If not a then not b."
The given conditional statement :" If my mom has to work, then I babysit my little sister.”
Then the contrapositive statement of the conditional statement will be
"If my mom does not have to work, then I do not babysit my little sister.”