Step-by-step explanation:
"average" or "mean value" are calculated by adding all data points up and dividing that sum by the number of data points.
e.g. if you eat 1 popsicle today, ate 2 popsicles yesterday and 3 the day before, you have 3 data points : 3, 2, 1.
in my example you had
(3 + 2 + 1)/3 = 6/3 = 2 popsicles every day on average.
the same principle here.
you have 2 days points. and your average score is
(88 + 93)/2 = 181/2 = 90.5