to compare, you have to make the fraction/mixed number into decimals
6&4/9=6.4444444444444
127/20=6.35
every decimal has a whole of 6, so you need to look at the tenth's place, 4 is obviously larger than 3, so 6&4/9 is the largest.
the other three numbers all have a 3 in its tenth's place, so look at the hundredth's place, 9 is larger than 7, and 7 is larger than 5
so from the least to the largest:
127/20, 6.375, 6.39. 6&4/9
