Two piles of sand, the first pile is 25 tons, and the second pile is 21 tons. After using up the same part of each of the two piles, the rest of the second pile is 3/4 of the first pile. How many tons are used in each pile? ．
两堆沙，第一堆25吨，第二堆21吨．这两堆中各用去同样多的一部分后，第二堆剩下的是第一堆的3/4，每堆用多去多少吨？．
<gadget id="calculator">25 - 21</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">4 / (1/4)</gadget>
<output>16</output>

<gadget id="calculator">25 - 16</gadget>
<output>9</output>

<result>9</result>