General solution algebra method or correspondence method.

Clever solution.

1, assuming that the total score of the method is 73× 100=7300, assuming that the average score of girls is 80, then 100 students * * * get 8000 points, 700 points more than the actual total score. This is because boys are higher than girls by 10 on average, so the extra 700 points are caused by the extra 10 points of each girl. It can be seen that girls are 700 and boys 10 = 30.

2. Proportioning method (73-70): (80-73) = 3: 7, 100/(7+3) × 3 = 30 people.