Subtract 3 (1/7) from 1, what is the difference?
从1里面减去3个(1/7)，差是多少？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">3 * (1/7)</gadget>
<output>3/7 = around 0.428571</output>

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

<result>4/7 = around 0.571429</result>