If 3x+8=20, then 0.5x+4.5=how much.
如果3x+8=20，那么0.5x+4.5=多少．
<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">0.5 * 4</gadget>
<output>2</output>

<gadget id="calculator">2 + 4.5</gadget>
<output>6.5</output>

<result>6.5</result>