✔ 最佳答案
Let x be the number of adults and y be the number of students
x+y=250(1)
50x+20y=6800(2)
From(1), x=250-y(3)
Put (3) into (2),
50x+20y=6800
50(250-y)+20y=6800
12500-50y+20y=6800
-30y= -5700
y=190
Put y=190 into (1)
x+y=250
x+190=250
x=60
So there are 60 adults and 190 students who attend the concert.