The distance between the two places is 15km. A and B start from the two places at the same time and walk toward each other. They meet after (5/3) hours. A travels 4km per hour, how many kilometers does B travel per hour?
两地相距15km，甲、乙两人从两地同时出发，相向而行，经过(5/3)小时相遇，甲每小时行4km，乙每小时行多少千米？
<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">15 / (5/3)</gadget>
<output>9</output>

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<result>5</result>