Cars A and B start at the same time from two places 280 kilometers apart, drive toward each other, and meet each other after 4 hours. Car A travels 30 kilometers per hour, how many kilometers per hour does Car B travel?
甲、乙两车从相距280千米的两地同时出发，相向而行，经过4小时两车相遇．甲车每小时行30千米，乙车每小时行多少千米？
<gadget id="calculator">280 / 4</gadget>
<output>70</output>

<gadget id="calculator">70 - 30</gadget>
<output>40</output>

<result>40</result>