Question

the sum of the digits of a two digit number is 9, also nine times this number is twice the number obtained by reversing the order of the digits . find the number.

Answer 1

the number is 18
sum=9
9 times the number=18×9=162 is twice the number obtained by reversing the order of the digits=81×2=162
HENCE PROVED

Answer 2

let digit at tens place is x and one's place is (9-x).
number is 9x+9.
number digit reversed is 90-9x.
9 (9x+9)=2 (90-9x)
x=1
number is 18.