How many four-digit numbers can be formed with the digits 3, 5, 7, 8, 9 which are greater than 8000,

Since the  number has to be greater than 8000, the thousand's place can be filled by only two digits, i.e. 8 and 9.

Now, the hundred's place can be filled with the remaining 4 digits as the repetition of the digits is not allowed.

The ten's place can be filled with the remaining 3 digits.

The unit's place can be filled with the remaining 2 digits.

Total numbers that can be formed $=2 \times 4 \times 3 \times 2=48$