(2/5)-(3/10)=((())/(()))-((())/(()))=how much.
(2/5)-(3/10)=((())/(()))-((())/(()))=多少．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) - (3/10)</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>