Question 1148319
Number {{{10t+u}}}


{{{system(t+u=15,t+10u-(10t+u)=9)}}}


{{{-9t+9u=9}}}
{{{-t+u=1}}}



Now simpler system is  {{{system(u+t=15,u-t=1)}}}.



{{{system(u=8,t=7)}}}



Number:   78