Divide the numerator of (20/35) by 5, how much should be subtracted from the denominator, so that the size of the fraction remains the same.
把(20/35)的分子除以5，分母应减去多少，才能使分数的大小不变．
<gadget id="calculator">35 / 5</gadget>
<output>7</output>

<gadget id="calculator">35 - 7</gadget>
<output>28</output>

<result>28</result>