odd number between 48 and 64. the tens digit is greater than the ones digit and the difference between the two digits is 4.
The numbers between 48 and 64 have either 4, 5 or 6 as their tens digit
which is larger by 4 than the ones digit.
Since the difference between the two digits is 4, it's either 40, 51, or 62,
and the only one that's odd and in the range between 48 and 64 is 51.
Edwin