SOLUTION: One of the digits of a two digits number is twice the other digit. the sum of the original number and the number formed by reversing the digits is 99. Find the number.
XY
+YX
99
To add two numbers and get an odd number like 9, one has to be
odd and the other even. And since one is twice the other and they
add to 9 they can only be 3 and 6. So it could be either
36 63
+63 or +36
99 99
It's either 36 or 63.
Edwin