For a one-digit decimal, if its decimal point is removed, it will be 18.9 more than the original. What is this one decimal place?
一个一位小数，如果把它的小数点去掉后，就比原来多18.9．这个一位小数是多少？
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">18.9 / 9</gadget>
<output>2.1</output>

<result>2.1</result>