The younger brother goes shopping at a speed of 6 kilometers per hour. After 2 hours, the mother has something to inform the younger brother, so she arranges the older brother to ride a bicycle to chase the younger brother. It is known that the elder brother rides a bicycle at a speed of 18 kilometers per hour, so how many hours will it take for the elder brother to catch up with the younger brother?
弟弟出门购物，出行的速度是每小时6千米，2小时后，妈妈有事要通知弟弟，所以安排哥哥骑车去追弟弟．已知哥哥骑车的速度是每小时18千米，那么，多少个小时后，哥哥能追上弟弟？
<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">2 / 12</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">6 * (1/6)</gadget>
<output>1</output>

<result>1</result>