Let the digits be x and y, so the number will be = (10x+y), on reversing the digits, the new number will be = (10y+x)
According to the question we can write as x =3y and also we can write as 10y+x+36=10x+y
Which implies 10y-y+36=10x-x
9y+36=9x
Now substituting the value of x
9y+36=27y
-18y=-36
y=2 and x=6
Now y=6+x=6+3=9
So the number is 62
To check: digit sum=6+2=8
Reversing the digit numbers becomes 26 and 26+36=62
Hence verified.