On a certain day in Urumqi, Xinjiang, the maximum temperature is 9°C, and the minimum temperature is -11°C. What is the temperature difference?
新疆乌鲁木齐市某一天最高气温是9℃，最低气温是-11℃，温差为多少．
<gadget id="calculator">9 + 11</gadget>
<output>20</output>

<result>20</result>