If you mean the average value (the mean) then add up the numbers=58 and divide by how many there are: 58/7=8.3 approx.
If you mean the mode, then put them in order:
1 3 3 6 9 18 18 and look for repeats: there are two modes: 3 and 18.
If you mean the median, then it’s the middle value: 6.
The range is 18-1=17.