Hey there!
Another word for the mean is the average. To calculate the mean in a set a numbers, you add up all of the numbers and then divide by the number of numbers!
8+5+9+5+5+7+3=42
We also have seven numbers in our data set, so we divide by seven!
42/7=6
Therefore, our mean is six!
I hope that this helps! Have a great day! :)