A bunch of watermelons, sell (1/4) and 6 of the total number for the first time, sell the remaining (1/3) and 4 for the second time, and sell the remaining (1/2) for the third time ) and 3 more, just sold out, how many watermelons are in this pile.
一堆西瓜，第一次卖出总个数的(1/4)又6个，第二次卖出余下的(1/3)又4个，第三次又卖出余下的(1/2)又3个，正好卖完，这堆西瓜原有多少个．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / (1/2)</gadget>
<output>6</output>

<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<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">10 / (2/3)</gadget>
<output>15</output>

<gadget id="calculator">15 + 6</gadget>
<output>21</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">21 / (3/4)</gadget>
<output>28</output>

<result>28</result>