Cars A and B start at the same time from places A and B, which are 210 meters apart, drive toward each other, and meet each other in 3 hours. It is known that car A travels 30 kilometers per hour, how many kilometers per hour does car B travel?
甲、乙两车从相距210米的A、B两地同时出发，相向而行，3小时相遇．已知甲车每小时行30千米，乙车每小时行多少千米？
<gadget id="calculator">210 / 3</gadget>
<output>70</output>

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

<result>40</result>