A rides a bicycle at 15 kilometers per hour, and B rides a bicycle at 12 kilometers per hour. It is known that B is ahead for 1.5 hours, how many hours can A catch up with B?
甲骑自行车每小时行15千米，乙骑自行车每小时行12千米．已知乙先行1.5小时，问几小时后甲可追上乙？
<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">1.5 / 3</gadget>
<output>0.5</output>

<gadget id="calculator">12 * 0.5</gadget>
<output>6</output>

<result>6</result>