Question 1169317
h, t, u
hundreds, tens, ones


Description may first give {{{system(h+t+u=12,(h+10t+100u)+198=100h+10t+u,h=t+u)}}}.


Some simplification:
{{{system(h+t+u=12,h-u=2,h=t+u)}}}

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After a few substitutions and algebra steps,
the number:  624