Here is a little list of adjectives that you could use to answer the question: excellent, great, very well, good, OK, not bad (I don't like this answer because it assumes that you are expecting things to be bad), so-so, not good, not well, terrible, and many others. But if you want to have fun with your answer, you can reply by saying "PERFECT". People are usually very surprised when you answer this way because it doesn't happen very often. Usually, the other person will smile when you answer this way. Try this way with your friends and watch their reactions...