Calculation: (4/5)-((4/5)-(1/2))-(1/5).
计算：(4/5)-((4/5)-(1/2))-(1/5)．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(4/5) - (1/2)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(4/5) - (3/10) - (1/5)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>