There are 28 seafarers on an ocean-going ship, and the fresh water on board can be used by all seamen for 40 days. 10 days after the ship left port, 12 foreign sailors were rescued on the high seas. How many days will the remaining fresh water be used by the people on board?
一艘远洋轮船上共有28名海员，船上的淡水可供全体海员用40天．轮船离港10天后在公海上救起12名遇难的外国海员，剩下的淡水可供船上的人用多少天．
<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">10 * (1/40)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(1/40) / 28</gadget>
<output>1/1_120 = around 0.000893</output>

<gadget id="calculator">28 + 12</gadget>
<output>40</output>

<gadget id="calculator">(1/1_120) * 40</gadget>
<output>1/28 = around 0.035714</output>

<gadget id="calculator">(3/4) / (1/28)</gadget>
<output>21</output>

<result>21</result>