A ship travels between A and B for 10 hours. The time ratio for the round trip is 2:3. When it comes back, the speed is 7 kilometers per hour slower. How many kilometers is the distance between A and B?
一艘船往返于A、B两地，共用了10小时，往返所用时间比是2：3，回来时时速慢7千米，A、B两地相距多少千米？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">10 * (2/5)</gadget>
<output>4</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">42 / 2</gadget>
<output>21</output>

<gadget id="calculator">21 * 10 * (2/5)</gadget>
<output>84</output>

<result>84</result>