Answer :

[tex]n-the\ number\\\\3(10n-3)=81\ \ \ \ |divide\ both\ sides\ by\ 3\\\\10n-3=27\ \ \ \ \ |add\ 3\ to\ both\ sides\\\\10n=30\ \ \ \ \ |divide\ both\ sides\ by\ 10\\\\\boxed{n=3}[/tex]

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