Question 144946
Assign variables to things you don't know.  Then write expressions based on the information given in the problem.

Let x = orchestra seat tickets sold
and y = balcony seat tickets sold

From:"The students sold 650 tickets" we get:
x + y = 650  <<--equation #1
Then, since the problem states the total in-take and costs of each ticket we get:
7.50x + 3.50y = 4375  <<--equation #2


Now you have two equations and two unknowns:
x + y = 650
7.50x + 3.50y = 4375

Solve the above with your favorite method (i.e., substitution method, cramer's rule, etc)