Answer:
x = 86
Explanation:
The average of a set of data is equal to the sum of the numbers divided by
number of the sample . In our case we have
98 , 99 , 86 , 89 , 70 and x the uknown, and we know that the average need to be 88 so
(98+99+86+89+70+x ) / 6 = 88
442 + x = 528
x = 528 - 442
x = 86