If a person travels 15 kilometers per hour from point A to point B, he can arrive 24 minutes early, but if he travels 12 kilometers per hour, he will arrive 15 minutes late. How much time was originally stipulated?
一个人从甲地到乙地，每小时行15千米，可以早到24分钟，如果每小时行12千米，就要迟到15分钟．求原来规定的时间是多少？
<gadget id="calculator">15 * 0.4</gadget>
<output>6</output>

<gadget id="calculator">12 * 0.25</gadget>
<output>3</output>

<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">9 / 3</gadget>
<output>3</output>

<result>3</result>