Add 16 to the denominator of (5/8), if the size of the fraction remains the same, how much should be added to the numerator.
(5/8)的分母加上16，要是分数的大小不变，分子应加上多少．
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<result>10</result>