(3/4) plus (2/5), minus (9/10), what is the difference?
(3/4)加上(2/5)的和，减去(9/10)，差是多少？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

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

<gadget id="calculator">(3/4) + (-1/2)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>