Crazy promotion on New Year's Day, 500 yo-yos, 200 were sold, how many yo-yos were left unsold.
元旦疯狂促销，500个悠悠球，卖掉200个，还剩多少的悠悠球没有卖．
<gadget id="calculator">500 - 200</gadget>
<output>300</output>

<gadget id="calculator">300 / 500</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>