Add 10 to the numerator of (5/7), to keep the fraction value unchanged, what should be added to the denominator
(5/7)的分子加上10，要使分数值不变，分母应是加上多少
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

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

<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<gadget id="calculator">21 - 7</gadget>
<output>14</output>

<result>14</result>