The construction site shipped 30 tons of cement, and all (1/5) of it was used up on the first day. How many tons are left?
建筑工地运来水泥30吨，第一天用去了全部的(1/5)，还剩多少吨？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">30 * (4/5)</gadget>
<output>24</output>

<result>24</result>