Thunderzips's Riddle no.1

if, x = 0,9999...
then 10x = 9,9999...
hence, 10x - x = 9x = 9,9999... - 0,9999...
so, 9x = 9
conclusion x=1

inconsistent isn't it?

If you know, where is the mistake,
awarded with 10 points maximum from me
:D