Well think of how many of your friends might ask you a particular question. If you posted a link to your profile on his page in social networks, the first, most likely, go at it people from your social circle.
Pay attention to the subject of the question. Remember, whether there is someone among your acquaintances who would ask him with the highest probability. Maybe someone of them already showed interest in the different moments of your life, and as soon as you posted the link to the profile of "Ask" or "Ask.FM", he immediately hurried to ask you a question anonymously.
In some cases, you can easily find out anonymous on "Ask" and "Ask.FM", if you look closely at the structure of the issue – capital or uppercase letters it is written, whether it has spelling and other errors, omitted necessary punctuation, as there are spaces between words. Read recent correspondence with your friends and compare them with how built this or that question. You will probably find similarities with the character of the letter of someone you know.
Remember, do not leave if you link to your profile on any websites, forums or social networks. Examine those who commented on the link or "liked" your post. Perhaps someone asked you a question.
Try to find out anonymous on "Ask" and "Ask.FM" remembering who you were asking questions on these resources, not your name. Maybe someone of them asked you anonymous question, however, on the subject of it is similar to what you have already been asked.
If you suspect one of your friends and really want to learn you are right or not, ask this person directly. It is unlikely he will resent it and will probably satisfy your curiosity. Some questions are asked with the purpose that the recipient himself realized who and what he wants to learn from him.
Be careful and don't trust the sites offering to download or buy programs that define anonymous. All of them are fraudulent created only for the purpose of defrauding money. In no case do not give anyone your login and password for the site.