=90-8÷[20÷5],

=90-2,

=88 (points);

Their actual average score is 88.

This problem belongs to the typical profit and loss problem. The key is to understand that the sum of profit and loss scores divided by the average score is the number of people taking the exam, which is the key to solve this problem.

Xiao Ming's score increased by 8 points, decreased by 12 points, and changed by (8+ 12)=20 points. The average scores were 90 points and 85 points respectively, and changed by (90-85)=5 points, so it can be seen that there are four people in 20÷5=4 (people). Answer like this. I hope the landlord will adopt it! ! Obviously, the average score is calculated!