What is the sum of (5/7) and (8/21) minus (2/21)?
(5/7)与(8/21)的和减去(2/21)，等于多少？
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">8 / 21</gadget>
<output>8/21 = around 0.380952</output>

<gadget id="calculator">2 / 21</gadget>
<output>2/21 = around 0.095238</output>

<gadget id="calculator">(8/21) - (2/21)</gadget>
<output>2/7 = around 0.285714</output>

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

<result>1</result>