I got 27.5 for the mean
mean: you add up all the #'s and divide them my their quantity( in other words by how many numbers there are)
In your case you have 8 numbers, you add them and divide them by 8!
Hope it helps ;)
I’m going to use Pythagorus theorem for his question. // firstly I would do 20^2 + 16^2 = 656 // we them square root that number, so the square root of 656 is 25.61, meaning the missing length is 25.6