The only fraction that can be simplified is 50/100.
31/100, 50/100, 67/100, 89/100 and 97/100 can not be simplified, as they can't be reduced any further. Since 50/100 is our only acceptable fraction, we can reduce it. Since 50 is half of the number 100, we can see that this can be reduced down to 1/2.
Any number that is half of a denominator is 1/2.
For ex.
3/6 = 1/2, 4/8 = 1/2 and 6/12 = 1/2.
As I said, we can not reduce the other fractions.
We can only reduce 50/100 to 1/2.
If this is not what you're looking for, i'm not sure what you are preferring to.