If the denominator of (4/5) is increased by 10, how much should the numerator be increased to keep the fraction value unchanged.
(4/5)的分母增加10，要使分数值不变，分子应增加多少．
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

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

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<result>8</result>