A number multiplied by 10 is 81 greater than the original number, what is the original number?
一个数乘10，比原来的数大81，原来的数是多少．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">81 / 9</gadget>
<output>9</output>

<result>9</result>