Find the difference between 9 (1/10) and 4 (1/10), what is the column formula
求9个(1/10)与4个(1/10)的差，列式是多少
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(9/10) - (2/5)</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>