Add 3 to the numerator of (3/5), how much should be added to the denominator to keep the fraction value unchanged.
(3/5)的分子加上3，要使分数值不变，分母应该加上多少．
<gadget id="calculator">3 + 3</gadget>
<output>6</output>

<gadget id="calculator">6 / 3</gadget>
<output>2</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<result>5</result>