Answer:
The best possible final average this student can get is 94.
Explanation:
The average score is given by the sum of the scores of all tests divided by the number of tests.
In this question:
First three tests: Mean score of 92, so total score of 92*3 = 276
Best possible score, with 4 tests:
In the first three, the total is 276. The best possible score is with a grade of 100 in the fourth test. The score will be:

The best possible final average this student can get is 94.