The voyage from port A to port B is 210 kilometers. It takes 6 hours for a ship to carry goods from port A to port B. When returning, it travels 7 kilometers more than when going there. How many hours does it take to return?
甲港到乙港的航程有210千米，一艘轮船运货从甲港到乙港，用了6小时，返回时每小时比去时多行7千米，返回时用了几小时？
<gadget id="calculator">210 / 6</gadget>
<output>35</output>

<gadget id="calculator">35 + 7</gadget>
<output>42</output>

<gadget id="calculator">210 / 42</gadget>
<output>5</output>

<result>5</result>