Add 6 to the numerator of (2/15), how much should the denominator be increased to keep the size of the fraction unchanged.
把(2/15)的分子加上6，要使分数的大小不变，分母应增加多少．
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">60 - 15</gadget>
<output>45</output>

<result>45</result>