By adding all your grades together and dividing it by the number of grades

ex) 100

96

100

the total is 296 and you divide that by 3 because 3 is the number of grades you have. Therefore your grade average is 98.6 which sums um to 99

ex) 100

96

100

the total is 296 and you divide that by 3 because 3 is the number of grades you have. Therefore your grade average is 98.6 which sums um to 99