Fortune-telling without a name _ How to calculate fortune-telling without a name?

Fortune tellers don't want birthdays, and don't ask their names. I wonder how he worked it out.

The calculation method of birthday is as follows: take your birthday girl, add 2 and 5 times 50, and then subtract your birth year to get a set of numbers. According to this figure, the fortune teller can calculate the year, month and day of your birth and the good or bad luck of your life. Counting surnames means covering your surnames with gossip. Needless to say, you don't have to show it to the fortune teller, he will know your last name.