The school bought 9 boxes of chalk, 20 pieces in each box, and used (1/3). How many useless sticks are left?
学校买9盒粉笔，每盒20支，用去(1/3)．还剩多少支没有用？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">20 * 9 * (2/3)</gadget>
<output>120</output>

<result>120</result>