If you add 5 to the numerator, the result is four-nineths. When the numerator is 4/9 of the denominator,

Add 13 to the numerator, and the result is two thirds, and the numerator is two thirds of the denominator.

In these two cases, the ratio of numerator to denominator is different: 2/3-4/9 = 6/9-4/9 = 2/9.

This is because the molecular phase difference is: 13-5 = 8.

8 is 2/9 of the denominator, and the denominator can be obtained: 8/(2/9) = 36.

So the molecule is: 36 * (4/9)-5 = 1 1.

Or: 36 * (2/3)-13 =11.

So the original score: 1 1/36.