There is a pile of coal, the total amount (2/5) is used on the first day, 18 tons are used on the second day, and the pile of coal (5/8) is used in two days, how many tons are used on the first day?
有一堆煤，第一天用去总数的(2/5)，第二天用去18吨，两天共用去这堆煤的(5/8)，第一天用去多少吨？
<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

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

<gadget id="calculator">(5/8) - (2/5)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">18 / (9/40)</gadget>
<output>80</output>

<gadget id="calculator">80 * (2/5)</gadget>
<output>32</output>

<result>32</result>