If the number obtained by subtracting 1 from the numerator and adding 1 to the denominator of a fraction is 0.8, what is the original fraction?
一个分数分子减1分母加1得到的数为0.8，则原来那个分数是多少．
<gadget id="calculator">1 / 0.8</gadget>
<output>1.25</output>

<result>1.25</result>