Missing Premise/Contrapositive ?

From my understanding, the contrapositive of a general principle have identical meanings. That being said, in the missing premise drills, if I put the the contrapositive as the answer to the missing premise is this consider correct or incorrect? For example: P: P: not B -> A C: X -> B For the the missing premise I would put X -> not A (with the contrapositive being A -> not X). The answer on the card would have A -> not X (with the contrapositive being X -> not A). Just wondering if it would make a difference which one is the contrapositive. Thanks for the help!