The average score of others can't be 9, so it depends on that number.

(92* 15+25* that number) divided by 40, the answer is the average score of their class.

The result of your calculation is 97.5, so if you calculate it in reverse, 97.5 * 40 = 3900, 92 * 15 = 1380, then 25 times their average score is equal to 3900- 1380=2520, if their average score is 2520.