A passenger boat sailing 13 kilometers per hour is sailing in a river, and the water speed of this river is 7 kilometers per hour, then how many hours does it take for the boat to travel 140 kilometers (going along the water).
一只每小时航行13千米的客船在一条河中航行，这条河的水速为每小时7千米，那么这只船行140千米需多少小时(顺水而行)．
<gadget id="calculator">13 + 7</gadget>
<output>20</output>

<gadget id="calculator">140 / 20</gadget>
<output>7</output>

<result>7</result>