There is a fraction that can be reduced to (1/4) if the numerator is added by 1; if the denominator is subtracted by 1, it can be reduced to (1/5). What is the fraction?
有一个分数，如果分子加1可约简为(1/4)；如果分母减1可约简为(1/5)，这个分数是多少．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">5 / 1</gadget>
<output>5</output>

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

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

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">3 / 1 / 16</gadget>
<output>3/16 = around 0.1875</output>

<result>3/16 = around 0.1875</result>