Question 1011629
The number is {{{10t+u}}} and the description directly translated into a system is
{{{system(t+u=9,(10u+t)-(10t+u)=45)}}}.


Simplifying the second equation relating the reversal,
10u-u+t-10t=45
9u-9t=45
u-t=5


System can be restated  {{{system(u+t=9,u-t=5)}}}.




<s>72</s>-----small mental mis-step when I solved the simple two-variable system.
Correct result IS  27.