【Question 7】
Subtract 101011 from 10000000000, and the digit 9 appears $\qquad$ times in the resulting answer.
【Analysis and Solution】
Number problem.
$$
1 \underbrace{000000000}_{10 \uparrow 0}-101011=\underbrace{999999999}_{10 \uparrow 9}-101010 \text {; }
$$
$\underbrace{9999999999}_{10 \text { nines }}-101010$ will not involve borrowing in any digit, and only the same digit position of $9-0$ will result in 9; $\underbrace{999999999}_{10 \uparrow 9}-101010$ results in an answer where the digit 9 appears $10-3=1$ times.