If x+5=8, then 2x+5=how much.
如果x+5=8，那么2x+5=多少．
<gadget id="calculator">8 - 5</gadget>
<output>3</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6 + 5</gadget>
<output>11</output>

<result>11</result>