Serial number for a product are to be made using 2 letters followed by 3 digitals. the letters are to be taken from 6 letters of the alphabet, with no repeats. the digitals are taken from 10 digitals (0, 1, 2, 9), with no repeat

Problem number 26 of the rhind papyrus says: find a quantity such that when it is added to of itself the result is a 15. the modern day equation that models this problem is x + x = 15. what is the solution to the equation? x = 10 x = 12 x = 15 x = 30