If a pile of sand is used up (3/4), exactly 15 tons are used. How many tons are there in this pile of sand?
一堆沙子，用去它的(3/4)，正好用去15吨，这堆沙子有多少吨？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">15 / (3/4)</gadget>
<output>20</output>

<result>20</result>