4/0.8-0.8/4=how much.
4/0.8-0.8/4=多少．
<gadget id="calculator">4 / 0.8</gadget>
<output>5</output>

<gadget id="calculator">0.8 / 4</gadget>
<output>0.2</output>

<gadget id="calculator">5 - 0.2</gadget>
<output>4.8</output>

<result>4.8</result>