3.12. The sum of the digits of a two-digit number is 12. If 36 is added to this number, the result is a number written with the same digits but in reverse order. Find the original number.
3.12 Let the desired number be of the form $10 x+y$. Then, by the condition,

$x+y=12$

and $10 x+y+36=10 y+x$, i.e.,

$x-y+4=0$.

Adding (1) and (2), we get $2 x=8$, hence $x=4$, and $y=8$.

Answer: 48.