2/3= 2/3*8/8 = 16/24 .
4/8 = 4/8*3/3= 12/24
There fore the rational no between 2/3 and 4/8 are 13/24, 14/24 , 15/24
U have to multiply the denominator of 2 no. From the first no. And similarly multiply the 2 no.from the denominator of the first no.and u should keep it in ur mind after multiplying the denominator of both the no.will be same then u can find the rational no.
I hope it will help uh. :)