Add 40 to the denominator of (3/8), how much should be added to the numerator to keep the size of the fraction unchanged.
(3/8)的分母加上40，要使分数的大小不变，分子应加上多少．
<gadget id="calculator">8 + 40</gadget>
<output>48</output>

<gadget id="calculator">48 / 8</gadget>
<output>6</output>

<gadget id="calculator">3 * 6</gadget>
<output>18</output>

<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<result>15</result>