If 4x+1=17, then 3x-1=how much.
如果4x+1=17，那么3x-1=多少．
<gadget id="calculator">17 - 1</gadget>
<output>16</output>

<gadget id="calculator">16 / 4</gadget>
<output>4</output>

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

<gadget id="calculator">12 - 1</gadget>
<output>11</output>

<result>11</result>