The road from A to B is about 300 kilometers long. Dad drove from A to B. It's been 2 hours. The remaining distance is 60 kilometers less than the distance traveled. What is the average speed at which Dad drives?
甲地到乙地的公路长约300千米，爸爸开车从甲地到乙地．已经行了2小时．剩下的路程比已经行的路程少60千米．爸爸开车的平均速度是多少？
<gadget id="calculator">300 + 60</gadget>
<output>360</output>

<gadget id="calculator">360 / 2 / 2</gadget>
<output>90</output>

<result>90</result>