The numerator of a fraction is 21, and (3/5) is obtained after division. What is the denominator of this fraction?
一个的分数的分子是21，经过约分后得(3/5)，则这个分数的分母是多少．
<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<gadget id="calculator">5 * 7</gadget>
<output>35</output>

<result>35</result>