For a pile of coal, 1/5 of the total amount is used for the first time, and 15 tons more than the first time is used for the second time, leaving 18 tons left. How many tons does this pile of coal weigh?
一堆煤，第一次用去总数的(1/5)，第二次比第一次多用15吨，还剩下18吨，这堆煤重多少吨？
<gadget id="calculator">18 + 15</gadget>
<output>33</output>

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

<gadget id="calculator">1 - (1/5) - (1/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">33 / (3/5)</gadget>
<output>55</output>

<result>55</result>