Cars A and B start at the same time from two places 320 kilometers apart, drive toward each other, and meet each other after 4 hours. A travels 30 kilometers per hour, how many kilometers per hour does B travel? (column equation solution)
甲、乙两车从相距320千米的两地同时出发，相向而行，经过4小时两车相遇．甲每小时行30千米，乙车每小时行多少千米？(列方程解答)
<gadget id="calculator">4 * 30</gadget>
<output>120</output>

<gadget id="calculator">320 - 120</gadget>
<output>200</output>

<gadget id="calculator">200 / 4</gadget>
<output>50</output>

<result>50</result>