Question 1188077
The number,  {{{100h+10t+u}}}


{{{system(u=h+t,abs(h-t)=6,100u+10t+h-(100h+10t+u)=99)}}}


{{{99u-99h=99}}}

{{{u-h=1}}}


Revising the system
{{{system(u=h+t,abs(h-t)=6,u-h=1)}}}


{{{system(u-h=t,abs(h-t),u-h=1)}}}
Looking at eq. 1 and eq. 3 here, value for {{{t}}} should be 1;
{{{highlight_green(t=1)}}}


{{{abs(h-t)=6}}}
Either {{{h-t=6}}}
Or
{{{h-t=-6}}}
--
If t=1, then {{{h-1=6}}}
{{{h=7}}}
or
{{{h=-6+1}}}----------this is no good.
-
{{{highlight_green(h=7)}}}


Finding the ones digit
{{{u=h+t}}}
{{{u=7+1}}}
{{{highlight_green(u=8)}}}