To find the mean you will have to add all the numbers and divide by how many numbers there are. In this case you would add:
10.09+10.14+10.29+10.07+9.99 = 50.58
So there 5 numbers if you count them...
Now you would divide 50.58 by 5 which gets you.....
10.116 which is the answer..
Have an awesome day and I hope this helped! <3