Last year (20 14), the crazy mobile phone number in the WeChat circle exposed your age. Please explain why with mathematical knowledge. If this is the case with 20 15,

Let the last digit of the mobile phone be X, (2x+5)*50+ 1764- year of birth; This is the algorithm of 20 14. You only need to change 1764 to 1765 to calculate the corresponding demerit of 20 15. Just kidding, 1765+250 = 20 15, and then subtract the year of birth from 20 15, naturally it is the age, and x times 2 times 50 is the hundred places, which will not affect the result. For people over 100, this so-called "algorithm" naturally fails.