On a map with a scale of 1:5,000,000, the measured distance from Lanzhou to Xi’an is 12 centimeters. Two cars A and B drove opposite each other at the same time and met after 4 hours. It is known that car A travels 80 kilometers per hour. How many kilometers does car B travel per hour?
在比例尺是1：5000000的地图上，测得兰州到西安的距离是12厘米，甲乙两辆汽车同时从两地相对开出，4小时后相遇，已知甲车的每小时行80千米，乙车每小时行多少千米？
<gadget id="calculator">1 / 5_000_000</gadget>
<output>1/5_000_000 = around 0</output>

<gadget id="calculator">12 / (1/5_000_000) / 100_000 / 4</gadget>
<output>150</output>

<gadget id="calculator">150 - 80</gadget>
<output>70</output>

<result>70</result>