Column calculation: (8/21)/(8/7)-87.5%*(5/21).
列式计算：(8/21)/(8/7)-87.5%*(5/21)．
<gadget id="calculator">8 / 21</gadget>
<output>8/21 = around 0.380952</output>

<gadget id="calculator">8 / 7</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">(8/21) / (8/7)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">87.5 / 100</gadget>
<output>0.875</output>

<gadget id="calculator">5 / 21</gadget>
<output>5/21 = around 0.238095</output>

<gadget id="calculator">0.875 * (5/21)</gadget>
<output>0.208333</output>

<gadget id="calculator">(1/3) - 0.208333</gadget>
<output>0.125</output>

<result>0.125</result>