Question

the two numbers whose sum is 9. if 27 is added to the number the digits are reversed . find the number

Answer 1

let x be the unit digit and y be the ten's digit 
acc to question
y+x=9                                                            ..1
10y+x+27=10x+y                                          
9x-9y=27                                                       ..2
from 1 and 2
x=6
y=3
and the no is 36

Answer 2

Let the number=10*x+y
sum of numbers=x+y=9_a
according to question-
10*x+y+27=10*y+x
9x-9y=-27
x-y=-3 _b
by solving eq a and b,we get x=3 and y=6
the number be=36