Simple calculation: (4/5)*(2/7)+(2/5)*(1/7).
简便运算：(4/5)*(2/7)+(2/5)*(1/7)．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(4/5) * (2/7)</gadget>
<output>8/35 = around 0.228571</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(2/5) * (1/7)</gadget>
<output>2/35 = around 0.057143</output>

<gadget id="calculator">(8/35) + (2/35)</gadget>
<output>2/7 = around 0.285714</output>

<result>2/7 = around 0.285714</result>