8.4/5/8*(5*2)=how much.
8.4/5/8*(5*2)=多少．
<gadget id="calculator">8.4 / 5 / 8</gadget>
<output>0.21</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">0.21 * 10</gadget>
<output>2.1</output>

<result>2.1</result>