For a true fraction, the numerator and denominator are two consecutive natural numbers. If 3 is added to the denominator, the fraction is (4/5). What is the original fraction?
一个真分数，分子、分母是两个连续自然数，如果分母加上3，这个分数是(4/5)，原来这个分数是多少．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * 4</gadget>
<output>16/5 = around 3.2</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(16/5) / (1/5)</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<gadget id="calculator">(16/5) / (1/5) / 17</gadget>
<output>16/17 = around 0.941176</output>

<result>16/17 = around 0.941176</result>