There are a bunch of candies, of which fruit candies account for (4/7), if 12 toffee candies are added. Fruit sugar only accounts for (2/5). How many candies were there in total?
有一堆糖果，其中水果糖占(4/7)，若再放入12颗奶糖．水果糖就只占(2/5)．这堆糖果原来一共有多少颗？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(4/7) - (2/5)</gadget>
<output>6/35 = around 0.171429</output>

<gadget id="calculator">(2/5) / (6/35)</gadget>
<output>7/3 = around 2.333333</output>

<gadget id="calculator">12 * (7/3)</gadget>
<output>28</output>

<result>28</result>