The number that is 9 more than 80% of a number is 10. What is this number?
比一个数的80%多9的数是10，这个数是多少？
<gadget id="calculator">10 - 9</gadget>
<output>1</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / (4/5)</gadget>
<output>5/4 = around 1.25</output>

<result>5/4 = around 1.25</result>