On Saturday morning, my sister and sister went to practice running. The elder sister runs 110 meters per minute, and the younger sister runs 80 meters per minute. The younger sister ran half an hour longer than the older sister, and ended up running 900 meters longer than the older sister. So how many meters did my sister run?
星期六早晨，姐姐和妹妹去练习跑步．姐姐每分钟跑110米，妹妹每分钟跑80米．妹妹比姐姐多跑了半小时，结果比姐姐多跑了900米．那么姐姐跑了多少米．
<gadget id="calculator">80 * 30</gadget>
<output>2_400</output>

<gadget id="calculator">2_400 - 900</gadget>
<output>1_500</output>

<gadget id="calculator">110 - 80</gadget>
<output>30</output>

<gadget id="calculator">1_500 / 30</gadget>
<output>50</output>

<gadget id="calculator">110 * 50</gadget>
<output>5_500</output>

<result>5_500</result>