(1-0.2)*(13-(3.12+5.28))=how much.
(1-0.2)*(13-(3.12+5.28))=多少．
<gadget id="calculator">1 - 0.2</gadget>
<output>0.8</output>

<gadget id="calculator">3.12 + 5.28</gadget>
<output>8.4</output>

<gadget id="calculator">13 - 8.4</gadget>
<output>4.6</output>

<gadget id="calculator">0.8 * 4.6</gadget>
<output>3.68</output>

<result>3.68</result>