There are 18 discs, how many of their (1/3) are more than their (1/9).
有18个圆片，它们的(1/3)比它们的(1/9)多多少个．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/3) - (1/9)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">18 * (2/9)</gadget>
<output>4</output>

<result>4</result>