After subtracting the numerator and denominator of (13/25) at the same time, it can be roughly divided into (1/4).
(13/25)的分子分母同时减去多少后，就可以约分为(1/4)．
<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) * 25</gadget>
<output>25/4 = around 6.25</output>

<gadget id="calculator">13 - (25/4)</gadget>
<output>27/4 = around 6.75</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(27/4) / (3/4)</gadget>
<output>9</output>

<result>9</result>