General question regarding causal conclusions

[gmatwork]

Hello,

When we have a causal conclusion such as

X---->Y

Will.... Not(X) ---> Not (Y) also be true?

If there is a question in which we need to strengthen a causal conclusion then if an answer choice does the second version then it strengthens the conclusion (OG 12 ed q 94). So does this imply the above?

[tim]

if X -> Y
then notY -> notX

this is always true; it is called the contrapositive. what you suggest is called the inverse and is not always true..