Stations A and B are 640 kilometers apart. Cars A and B drive towards each other at the same time. They meet after 8 hours. The speed of car A is 30 km/h. What is the speed of car B?
甲、乙两站相距640千米，A、B两车同时从两站相向开出，8小时后相遇，A车的速度是30千米/时，B车的速度是多少？
<gadget id="calculator">640 / 8</gadget>
<output>80</output>

<gadget id="calculator">80 - 30</gadget>
<output>50</output>

<result>50</result>