Every day Lin Hong leaves home at 7:20 and arrives at school at 7:40. How long does it take her to go to school every day?
每天林红7：20从家出发，7：40到校，她每天在上学的路上用多长时间？
<gadget id="calculator">40 - 20</gadget>
<output>20</output>

<result>20</result>