If 4x=16.8, then 20-3x=how much.
如果4x=16.8，那么20-3x=多少．
<gadget id="calculator">16.8 / 4</gadget>
<output>4.2</output>

<gadget id="calculator">3 * 4.2</gadget>
<output>12.6</output>

<gadget id="calculator">20 - 12.6</gadget>
<output>7.4</output>

<result>7.4</result>