Car A and Car B drive from opposite sides at the same time. Car A travels 50 kilometers per hour. After 3 hours, it has passed the midpoint of 30 kilometers. At this time, car A and car B are still 6 kilometers apart. Ask for car B. How many kilometers per hour?
甲、乙两车同时从两地相向开出，甲车每小时行50千米，经过3小时已驶过中点30千米，此时甲车与乙车还相距6千米，求乙车每小时行多少千米？
<gadget id="calculator">50 * 3</gadget>
<output>150</output>

<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<gadget id="calculator">150 - 60 - 6</gadget>
<output>84</output>

<gadget id="calculator">84 / 3</gadget>
<output>28</output>

<result>28</result>