The mean is the sum of all data divided by the number of data.
You have 6 data:
Mean: 90.7
-----------------------------------------------
The Median is the data in the middled of the data when the data is froms least to greatest.
In this case as the number of data is 6 you take third and fourth data and find the average (sum the data and divide into 2):
Median: 89.5
----------------------------------
The mode is the data that appears the most:
Mode:98
----------------------
The Range is the difference between the largest and the smallest data.
Range: 16