Mean:
Sum all the data and divide into number of data (8):

Mean: 78.1
Median:
Order from less to geatest the data:

As the number of data is an odd number you chosse the two terms in the middle and find the average (sum the terms and divide into 2):

Median: 77
Mode:
The mode is the data that repeat most times.
In this case the data 77 repeats 3 times
Mode: 77
Range:
Substract the smallest number from the largest number:

Rangle: 79