(2/15) can be roughly divided into (1/3) after adding the numerator and denominator at the same time.
(2/15)分子和分母同时加上多少后就可以约分为(1/3)．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/3) * 15</gadget>
<output>5</output>

<gadget id="calculator">5 - 2</gadget>
<output>3</output>

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

<gadget id="calculator">3 / (2/3)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>