Question 1208385
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I would phrase it like this
D = {x | x is an integer and 0 ≤ x ≤ 9}


Your math textbook may write it like this
*[Tex \Large D = \left\{\text{x} | \text{x} \in \mathbb{Z}, \ 0 \le \text{x} \le 9 \right\}]
The portion *[Tex \large \text{x} \in \mathbb{Z}] translates to "x is in the set of integers" i.e. "x is an integer".
Why is Z used for the set of integers? The Z stands for Zahl, which is a German word meaning "number".
More info found here
<a href="https://mathworld.wolfram.com/Z.html">https://mathworld.wolfram.com/Z.html</a>
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