Two cars, A and B, leave from Chengdu and Chongqing at the same time and meet each other after 3 hours. Car A travels 80 kilometers per hour. When they meet, A passes the midpoint of Chengdu and Chongqing for 30 kilometers. How many kilometers does car B travel per hour?
甲乙两车分别从成渝两地同时相对开出，3小时后相遇，甲车每小时80km，相遇时，甲过了成渝两地中点30km，乙车每小时行多少km？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 * (2/3)</gadget>
<output>20</output>

<gadget id="calculator">80 - 20</gadget>
<output>60</output>

<result>60</result>