When 2X+1=10, 4X+1=how much.
当2X+1=10时，4X+1=多少．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">4 * (9/2)</gadget>
<output>18</output>

<gadget id="calculator">18 + 1</gadget>
<output>19</output>

<result>19</result>