(1/13) can be roughly divided into (1/3) after adding how much to the numerator and denominator at the same time.
(1/13)的分子和分母同时加上多少后就可以约分为(1/3)．
<gadget id="calculator">3 / 1</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">13 / 1</gadget>
<output>13</output>

<gadget id="calculator">(1/3) * 13</gadget>
<output>13/3 = around 4.333333</output>

<gadget id="calculator">(13/3) - 1</gadget>
<output>10/3 = around 3.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(10/3) / (2/3)</gadget>
<output>5</output>

<result>5</result>