This one is quite easy since it is whole numbers. Tens are made out of 10 ones, that is a ten! Add another ten which would equal 20 ones. Add 76 and 20 ones and that would equal 96!
76 ones + 20 ones = 96 ones or 9 tens and 6 ones 76 ones + 2 tens = 96 ones or 9 tens and 6 ones
It's very simple. Here is a place value digit concept.
76 - 7 is a ten, 6 is ones.
Now, right on to the question. The answer would be 96 or 9 tens and 6 ones or 96 ones. Either those are fine.
I've also listed some attachments to help you out.
So to find the mean you add them all together and divide by the number of numbers there is so 11+15+19+17+23+20+17+18+21=174 and there are 10 numbers so it would be 174/10 which is 17.4 so you answer is 17.4