Since ur using r as a variable the answer is r = 7.
So since there is a mixed number, 8 means there are 8 one-hundreds and 23 remaining ones. So, 800+23=823 ones. 823/100 as an improper fraction. since it is already out of 100, your job is easy. you now divide 823 by 100 (move the decimal over to the left 2 places) and you get 8.23 as a decimal. Hope i helped!!
The mean is the average you're used to, where you add up all the numbers and then divide by the number of numbers. The median is the middle value in the list of numbers. Mode is the number which appears most often in a set of numbers.
Hope this helps you :)