A number of 50 digits has all its digits equal to 1 except the 26th digit. If the number is divisible by 13, then find the digit in the 26th place.
(In reply to re: Re so easy
Take a number, say 652 . When you say its first digit is 6 second is 5 etc you count from left to right.
That's the way I did it. ( i did it my way..)
Of course you are free to define it the other way
and then X1=91 ===> X=9 .
So you and I solved two problems for the price of one.