To have an average of 92 with four tests, you have to multiply 92 by 4 to find the total score.

The total score must be 368. Three of the scores are given. Add the three scores and subtract that from 368.

The total of the three scores is 278. The total must be 368. Subtract 278 from 268 to find the missing score.

The student must have a score of 90 to have an average score of 92.