If a person travels from A to B in 12 hours, how many more hours does it take to return to slow down (1/5).
某人用12小时从甲地去乙地，返回时需多用多少小时，速度才可减慢(1/5)．
<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<result>3</result>