For a pile of sand, 1/5 of the total amount was removed on the first day, and 4.5 tons more of the total amount (1/4) was removed on the second day, and the remaining 12 tons were shipped out on the third day. This pile of sand has a total of How many tons?
一堆沙子，第一天运走总数的(1/5)，第二天运走总数的(1/4)还多4.5吨，剩下12吨第三天全部运完，这堆沙子一共有多少吨？
<gadget id="calculator">4.5 + 12</gadget>
<output>16.5</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/5) - (1/4)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">16.5 / (11/20)</gadget>
<output>30</output>

<result>30</result>