How much is 1/2 less than 1/3 or more than 1/2?
If you want to write a fraction between two other fractions, average the numerators and denominators.
There is an example.If both fractions are the same sign, a fraction between a/b and c/d is (a+c)/(b+d).This is a useful exercise for the literate.
There are many fractions which meet these conditions, but this general rule will always guarantee to find one.