The number of longan trees in the orchard accounts for (3/7) of all fruit trees. After planting 4 more longan trees, the number of longan trees accounts for (1/2) of all fruit trees. How many longan trees are there now?
果园里龙眼树的棵数占全部果树棵数的(3/7)，再种植4棵龙眼树后，这时龙眼树棵数占全部果树的(1/2)，现在有龙眼树多少棵？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">(3/7) * 4</gadget>
<output>12/7 = around 1.714286</output>

<gadget id="calculator">4 - (12/7)</gadget>
<output>16/7 = around 2.285714</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) - (3/7)</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(16/7) / (1/14)</gadget>
<output>32</output>

<gadget id="calculator">32 * (1/2)</gadget>
<output>16</output>

<result>16</result>