Increase the numerator of (4/9) by 12, how much should the denominator be increased to make the fraction equal to (1/2).
把(4/9)的分子增加12，要使分数值等于(1/2)，分母应增加多少．
<gadget id="calculator">4 + 12</gadget>
<output>16</output>

<gadget id="calculator">2 / 1</gadget>
<output>2</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<gadget id="calculator">32 - 9</gadget>
<output>23</output>

<result>23</result>