If a number is multiplied by 11, the product obtained is 90 more than the original number. What is the number?
一个数乘11，得到的积比原来的数多90，这个数是多少．
<gadget id="calculator">11 - 1</gadget>
<output>10</output>

<gadget id="calculator">90 / 10</gadget>
<output>9</output>

<result>9</result>