Answer:
If you are not busy on Saturday night, then you do not baby-sit on Saturday night
Explanation:
For a conditional if P then Q, the contrapositive is if not Q, then not P.
For the given conditional, ...
P = you baby-sit on Saturday night
Q = you are busy on Saturday night
So, the contrapositive is ...
If you are not busy on Saturday night, then you do not baby-sit on Saturday night.