There is a pile of yellow sand, first use up (2/5), and then use up 15 tons, then the remaining yellow sand is as much as used. How many tons is this pile of yellow sand?
有一堆黄沙，先用去(2/5)，又用去15吨，这时剩下的黄沙和用去的一样多．这堆黄沙原来有多少吨？
<gadget id="calculator">15 + 15</gadget>
<output>30</output>

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

<gadget id="calculator">1 - (2/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">30 / (1/5)</gadget>
<output>150</output>

<result>150</result>