How many (1/7) are added to (3/7) is 1.
(3/7)再添上多少个(1/7)是1．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 - (3/7)</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(4/7) / (1/7)</gadget>
<output>4</output>

<result>4</result>