7. Consider a positive integer,
$$
\mathrm{N}=9+99+999+\ldots \ldots+\underset{2018}{999 \ldots 9}
$$

How many times does the digit 1 occur in its decimal representation?
\begin{tabular}{l|l} 7 & We have \end{tabular}
$$
\begin{array}{l}
=111 \ldots 100000+(11110-2018) \\
2014 \\
=\underset{2014}{111 \ldots 100000}+9092 . \\
\end{array}
$$

Hence in decimal representation there are 2014 ones.