Question 985179
10t+u, original number


{{{system(t=2u,10u+t=-36+10t+u)}}}


Simple substitution.


{{{10u-u=-t+10t-36}}}
{{{9u=9t-36}}}
{{{9u=9(2u)-36}}}
{{{9u-18u=-36}}}
{{{u=4}}}
-
{{{t=2u}}}
{{{t=8}}}


Number was 84.