If x+1.5=7.5, then 2.1x=how much.
如果x+1.5=7.5，那么2.1x=多少．
<gadget id="calculator">7.5 - 1.5</gadget>
<output>6</output>

<gadget id="calculator">2.1 * 6</gadget>
<output>12.6</output>

<result>12.6</result>