A batch of cement weighs 30 tons, 30% of the total amount is used for the first time, and 1/6 of the total amount is used for the second time, how many tons of cement are left?
一批水泥重30吨，第一次用去总数的30%，第二次用去总数的(1/6)，还剩下多少吨水泥？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (3/10) - (1/6)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">30 * (8/15)</gadget>
<output>16</output>

<result>16</result>