the answer is 85 let me explain:
All you do for the mean is add all the values(numbers) together, and then divide by the amount o f numbers.
so your number set is
87,84,86,79,84,90
so all we do is add them all together
87 + 84 + 86 + 79 + 84 + 90
which equals 510
then we divide by the amount of values (numbers) there are.
since there are 6 numbers in this data set we have to divide 510 by 6
which gives us a quotient of 85
so 85 is your answer.
