2 63/60

To subtract these mixed numbers, we first need to convert the fractions to have a common denominator. In this case, the least common denominator is 60.

7 9/20 = 7 + 27/60 = 7 27/60
5 17/30 = 5 + 34/60 = 5 34/60

Now we subtract the two mixed numbers:

7 27/60 - 5 34/60 = 2 27/60 - 34/60
= 2 27/60 - 34/60
= 2 27 - 34/60
= 2 27 - 34/60
= 2 63/60

Therefore, 7 9/20 - 5 17/30 = 2 63/60.