Add 10 to the denominator of (4/5), what is the numerator to keep the fraction constant?
(4/5)的分母加上10，要使分数的大小不变，分子应多少．
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

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

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

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

<result>8</result>