Question

they didn't say no is reversed it is mentioned as digits are reversed then how this is possible

Answer 1

Let a number of two digits be written as xy.
where x is on 10th place and y on unit place.

Let's have an example. .
Suppose there is number 23 .where x = 2 and y=3. then, to form a number we have to Write it as 20 + 3 = 23,
Again, we know that 10th place has value of 10 and unit has 1 .

We can write 23 = 10×(digit of 10th place) + 1(digit of unit place) = 10(2) +3 = 23
if we reverse number it will be 32 ,
and it can be written as 10(3) +2 = 32.

Similarly if number is written as xy then,
Number will be = 10x +y

Reverse of number = 10y + x

Remember xy is not a Number , it is representation of following number.
x and y are digits .
Therefore,
sum of digits means sum of x and y
x + y = 5

Number = reverse of number + 9
10x +y = 10y +x +9
On solving both equations we get,
x = 3
y = 2
Number will be 10x +y = 23
Note:- xy ≠ x × y Since 23 ≠ 2×3

Hope now it is clear to you.:-)