Questions asked in the negative are often confusing. In addition, in some cultures, there is a tendency to avoid disagreement and use of the word "no". For example, I asked, "If I share the secret, you won't tell, will you?" A Chinese person will often respond "yes". Of course, the expected answer is "no". Therefore, to be clear, a person must say more than a simple yes or no. "Can't you play the piano?" "Yes, I can." "No, I can't."

yes (I can) No (I can't) this question means very nearly same as "you can play piano, right?", it's being bit less presumptuous, more polite, than "can you play a piano?" However, if this negation confuses you, you can avoid using yes/no answer altogether and go with "I can" or "I can't"