Answer: The number of people bought their tickets online = 450 and the number of people bought their tickets offline = 550 .
Explanation:
Let x = Number of tickets sold online.
y= Number of tickets sold at the door.
As per given , we have the following linear equation:

Put value of y from (1) in (2) , we get

Put value of x in (1), we get

Hence, the number of people bought their tickets online = 450 and the number of people bought their tickets offline = 550 .