If 5x-9=3.5, then 4x+8=how much.
如果5x-9=3.5，那么4x+8=多少．
<gadget id="calculator">9 + 3.5</gadget>
<output>12.5</output>

<gadget id="calculator">12.5 / 5</gadget>
<output>2.5</output>

<gadget id="calculator">4 * 2.5</gadget>
<output>10</output>

<gadget id="calculator">10 + 8</gadget>
<output>18</output>

<result>18</result>