What is the sum of (1/5) and (2/7) subtracted from 1?
1减去(1/5)与(2/7)的和，得数是多少？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(1/5) + (2/7)</gadget>
<output>17/35 = around 0.485714</output>

<gadget id="calculator">1 - (17/35)</gadget>
<output>18/35 = around 0.514286</output>

<result>18/35 = around 0.514286</result>