Find the probability of using debit card Our professor gave this question as assignment, My question is does this question have all information needed to solve it? I asked her and she said it has all information but still I cannot figure out how I can solve it with just knowing the probability of using debit card in supermarket. Can someone please provide me a tip on how I can solve this question with this information or is it solvable?

According to a recent Interact survey, 28% of consumers use their
  debit cards in supermarkets. Find the probability that they use debit
  cards in only other stores or not at all.

 A: The intended answer is mostly likely $72\%$.  This is because to say that a consumer uses his/her debit cards "in only other stores or not at all" is logically equivalent to saying that he/she does not use his/her debit cards in supermarkets.  So if $28\%$ of consumers do use their debit cards in supermarkets, then $72\%$ do not.
That said, the problem strikes me as not well worded.  In giving the answer of $72\%$, I am assuming that what's meant by "the probability that they use debit cards..." is the probability that a randomly selected individual consumer uses his/her debit cards only in other stores or not at all.  As stated, however, it's asking about the probability that an entire collection of consumers use their debit cards in a certain way.  Whether you read the "they" as referring to the entire set of consumers, or just to the $28\%$ who use them at supermarkets (as quasi's answer does), the answer is $0$.  It's possible the person writing the question really meant it this way, as quasi suggests; I think it's more likely they were just a bit sloppy in their wording.  I know I sometimes am.
