(2/5)*(1/2)-X=(1/5).
(2/5)*(1/2)-X=(1/5)．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">(2/5) * (1/2)</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) - (1/5)</gadget>
<output>0</output>

<result>0</result>