What's a mixed number between 17/5 and 7/2

All you've got to do is divide the numerator by the denominator to get the mixed number. The mixed number is likely not to come out as a whole number though, so just see how many times the numerator can go into the denominator and put the remainder as the numerator over the fraction.

17/5
Since 5 can go into 17 three times as a whole, put the remainder(2) as the numerator
Final  3 2/5

7/2
Since 2 can go into 7 three times as a whole, put the remainder(1) as the numerator
Final  3 1/2