520 students in the third grade participated in the autumn outing. The number of people who have already started is 20 times more than the number of people who have not started. How many people have not yet started?
三年级520名同学参加秋游，已出发的人数比没出发人数的9倍多20人，现在没有出发的还有多少人．
<gadget id="calculator">520 - 20</gadget>
<output>500</output>

<gadget id="calculator">1 + 9</gadget>
<output>10</output>

<gadget id="calculator">500 / 10</gadget>
<output>50</output>

<result>50</result>