Two people, A and B, walk toward each other from A and B at the same time, and A travels 12 kilometers per hour. After 4 hours, A travels 8 kilometers longer than B. How many kilometers does B travel per hour?
甲乙两人同时从A，B两地相向而行，甲每小时行12千米．4小时后，甲比乙多行8千米．乙每小时行多少千米？
<gadget id="calculator">12 * 4</gadget>
<output>48</output>

<gadget id="calculator">48 - 8</gadget>
<output>40</output>

<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<result>10</result>