Add 18 to the denominator of (5/9), how much should be added to the numerator to keep the size of the fraction constant
(5/9)的分母加上18，要使分数的大小不变，分子应加上多少
<gadget id="calculator">9 + 18</gadget>
<output>27</output>

<gadget id="calculator">27 / 9</gadget>
<output>3</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

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

<result>10</result>