Zhang Jian and Chen Shi rode bicycles from the same place to opposite directions. After 1.5 hours, the distance is 37.5 kilometers, Chen Shi travels 12 kilometers per hour, how many kilometers does Zhang Jian travel per hour?
张坚和陈实骑自行车从同一地点向相反方向骑去．1.5小时后相距37.5千米，陈实每小时行12千米，张坚每小时行驶多少千米？
<gadget id="calculator">12 * 1.5</gadget>
<output>18</output>

<gadget id="calculator">37.5 - 18</gadget>
<output>19.5</output>

<gadget id="calculator">19.5 / 1.5</gadget>
<output>13</output>

<result>13</result>