Given:
The linear function for average test score in your math class is

where x is the number of the test taken.
The linear function g(x) in the given table represents the average test score in your science class, where x is the number of the test taken.
To find:
Part A: The test average for your math class after completing test 2.
Part B: The test average for your science class after completing test 2.
Part C: Which class had a higher average after completing test 4?
Solution:
Part A:
We have,

Put x=2 in the above function, to find the test average for your math class after completing test 2.



Therefore, the test average for your math class after completing test 2 is 80.8.
Part B:
From the given table it is clear that g(x) =79 at x=2.
Therefore, the test average for your science class after completing test 2 is 79.
Part C:
Put x=4 in f(x), to find the test average for your math class after completing test 4.



From the table it is clear that the value of g(x) is increased by 1 as x is increased by 1. So, the value of function g(x) at x=4 must be 1 more than 80.

It is clear that,

Therefore, math class had a higher average after completing test 4.