(3/10)*((5/7)-(10/21)).
(3/10)*((5/7)-(10/21))．
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">10 / 21</gadget>
<output>10/21 = around 0.47619</output>

<gadget id="calculator">(5/7) - (10/21)</gadget>
<output>5/21 = around 0.238095</output>

<gadget id="calculator">(3/10) * (5/21)</gadget>
<output>1/14 = around 0.071429</output>

<result>1/14 = around 0.071429</result>