After subtracting 6 from the numerator of (9/15), how much should the denominator be subtracted to keep the size of the fraction unchanged.
(9/15)的分子减去6后，要使分数的大小不变，分母要减去多少．
<gadget id="calculator">9 - 6</gadget>
<output>3</output>

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

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

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

<result>10</result>