The numerator and denominator of a true fraction are two continuous natural numbers. If the denominator is added with 3, the number becomes 4 / 4 of the total, what is the original fraction?

The numerator and denominator of a true fraction are two continuous natural numbers. If the denominator is added with 3, the number becomes 4 / 4 of the total, what is the original fraction?

Let the denominator be X
(x-1)/(x+3)=4/5
4x+12=5x-5
x=17
The original score is 16 / 17