The denominator of (15/18) is reduced by 6, what should be the numerator to keep the size of the fraction constant.
(15/18)的分母减少6，要使分数的大小不变，分子应该是多少．
<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<gadget id="calculator">12 / 18</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">15 * (2/3)</gadget>
<output>10</output>

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

<result>5</result>