Add 10 to the denominator of (3/5), how much should be added to the numerator to keep the size of the fraction unchanged.
把(3/5)的分母加上10，要使分数的大小不变，分子应加上多少．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 - 3</gadget>
<output>6</output>

<result>6</result>