The younger brother started from home and walked to the park at a speed of 6 kilometers per hour. Two hours later, the elder brother left home and rode a bicycle at a speed of 18 kilometers per hour to chase his younger brother. Ask how many hours later you can catch up with your brother.
弟弟以每小时6千米的速度从家里出发步行去公园，2小时后，哥哥离开家以每小时18千米的速度骑车去追赶弟弟．问多少小时后能追上弟弟．
<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>