There are only fruit candies and toffee in a bag of candies, of which fruit candy accounts for (1/3). After adding 18 pieces of toffee, fruit candy accounts for (2/9). How many pieces of toffee are there in this bag of candies?
一包糖只有水果糖和奶糖，其中水果糖占(1/3)，再放入18块奶糖后，水果糖占(2/9)，这包糖果原来有多少块奶糖．
<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

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

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) - (2/9)</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">4 / (1/9)</gadget>
<output>36</output>

<gadget id="calculator">36 * (1/3)</gadget>
<output>12</output>

<result>12</result>