Question 1000886
{{{10t+u}}}, is the number.


{{{t=u/3}}} from description, which gives automatically certain possible combinations for u and t.  Those you can easily identify:
{{{t/u=1/3=2/6=3/9}}}, shows three possible combinations as a ratio.


Next part gives  {{{(10u+t)-(10t+u)=2+(t+u)}}} when carefully analyzed and transcribed into the equation.


The rest is for you to do.  Hopefully, no trouble.