Question 314197
There are two variables:

Let x = the number of $6 tickets
Let y = the number of $9 tickets


You need two equations.


Total sales were $10,500, so


Equation 1: 6x +9y = 10500


There were 250 more student tickets sold than nonstudent tickets, so


Equation 2: x = y + 250


Now take x=y+250 from Equation 2 and substitute it into Equation 1:


6(y+250) +9y = 10500
6y+1500 +9y = 10500
15y = 10500-1500
15y=9000
y=600


Now find x:


x=y+250
x=600+250
x=850


There were 850 student tickets and 600 nonstudent tickets.