Numbers with 8 digits:
\begin{aligned}
&=99999999-10000000\\
&=89999999+1\\
&=90000000
\end{aligned}
Numbers with 4 digits:
&=9999-1000\\
&=8999+1\\
&=9000
Nine crore
Nine thousand
On subtracting them, we get:
&=90000000-9000\\
&=89991000
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