From the school to the Children's Palace, the elder brother has to walk for 20 minutes, and the younger brother has to walk for 30 minutes. If the younger brother walks 5 minutes earlier than the older brother, how many minutes will it take for the older brother to catch up with the younger brother?
从学校到少年宫，哥哥要走20分钟，弟弟要走30分钟．如果弟弟比哥哥早走5分钟，哥哥追上弟弟需要多少分钟．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">(1/6) / (1/60)</gadget>
<output>10</output>

<result>10</result>