Subtract 2 from the numerator of (5/8), how much should the denominator be subtracted to keep the fraction constant.
(5/8)的分子减去2，要使分数大小不变，分母应减多少．
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">8 * (3/5)</gadget>
<output>24/5 = around 4.8</output>

<gadget id="calculator">8 - (24/5)</gadget>
<output>16/5 = around 3.2</output>

<result>16/5 = around 3.2</result>