If 4x+3=15, then 3x+4=how much.
如果4x+3=15，那么3x+4=多少．
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

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

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 + 4</gadget>
<output>13</output>

<result>13</result>