You can
put this solution on YOUR website!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)