Car A and car B are 20 kilometers apart. Car B is in front and car A is behind. The two cars start at the same time. After 2 hours, car A catches up with car B. It is known that car B travels 50 kilometers per hour. How much does car A travel per hour? km.
甲乙两车相距20千米，乙车在前，甲车在后，两车同时出发，2小时后甲车追上乙车，已知乙车每小时行50千米，甲车每小时行多少千米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">50 + 10</gadget>
<output>60</output>

<result>60</result>